src: Add patch to disable -Wenum-enum-conversion

We add KCFLAGS=-Wno-error to turn off -Werror but unfortunately, there
are some files that turn on -Werror unconditionally, which breaks the
build. Add the patch that will disable -Wenum-enum-conversion for the
normal kernel, which is a part of the 6.9 Kbuild pull request.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

src/75b5ab134bb5f657ef7979a59106dce0657e8d87.patch

@@ -0,0 +1,69 @@
+From 75b5ab134bb5f657ef7979a59106dce0657e8d87 Mon Sep 17 00:00:00 2001
+From: Nathan Chancellor <nathan@kernel.org>
+Date: Tue, 5 Mar 2024 15:12:47 -0700
+Subject: kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1
+
+Clang enables -Wenum-enum-conversion and -Wenum-compare-conditional
+under -Wenum-conversion. A recent change in Clang strengthened these
+warnings and they appear frequently in common builds, primarily due to
+several instances in common headers but there are quite a few drivers
+that have individual instances as well.
+
+  include/linux/vmstat.h:508:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
+    508 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+        |                            ~~~~~~~~~~~~~~~~~~~~~ ^
+    509 |                            item];
+        |                            ~~~~
+
+  drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:955:24: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
+    955 |                 flags |= is_new_rate ? IWL_MAC_BEACON_CCK
+        |                                      ^ ~~~~~~~~~~~~~~~~~~
+    956 |                           : IWL_MAC_BEACON_CCK_V1;
+        |                             ~~~~~~~~~~~~~~~~~~~~~
+  drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:1120:21: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
+   1120 |                                                0) > 10 ?
+        |                                                        ^
+   1121 |                         IWL_MAC_BEACON_FILS :
+        |                         ~~~~~~~~~~~~~~~~~~~
+   1122 |                         IWL_MAC_BEACON_FILS_V1;
+        |                         ~~~~~~~~~~~~~~~~~~~~~~
+
+Doing arithmetic between or returning two different types of enums could
+be a bug, so each of the instance of the warning needs to be evaluated.
+Unfortunately, as mentioned above, there are many instances of this
+warning in many different configurations, which can break the build when
+CONFIG_WERROR is enabled.
+
+To avoid introducing new instances of the warnings while cleaning up the
+disruption for the majority of users, disable these warnings for the
+default build while leaving them on for W=1 builds.
+
+Cc: stable@vger.kernel.org
+Closes: https://github.com/ClangBuiltLinux/linux/issues/2002
+Link: https://github.com/llvm/llvm-project/commit/8c2ae42b3e1c6aa7c18f873edcebff7c0b45a37e
+Acked-by: Yonghong Song <yonghong.song@linux.dev>
+Signed-off-by: Nathan Chancellor <nathan@kernel.org>
+Acked-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
+---
+Link: https://git.kernel.org/masahiroy/linux-kbuild/c/75b5ab134bb5f657ef7979a59106dce0657e8d87
+---
+ scripts/Makefile.extrawarn | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
+index a9e552a1e9105b..2f25a1de129d10 100644
+--- a/scripts/Makefile.extrawarn
++++ b/scripts/Makefile.extrawarn
+@@ -132,6 +132,8 @@ KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
+ KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
+ KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
+ KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
++KBUILD_CFLAGS += -Wno-enum-compare-conditional
++KBUILD_CFLAGS += -Wno-enum-enum-conversion
+ endif
+
+ endif
+-- 
+cgit 1.2.3-korg
+