powerpc/Makefile: Remove workaround for gcc versions below 4.9

Commit 6ec4476 ("Raise gcc version requirement to 4.9")
made it impossible to build with gcc 4.8 and under.

Remove related workaround.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a1e552006b8c51f23edd2f6cabdd9a986c631146.1615380184.git.christophe.leroy@csgroup.eu

arch/powerpc/Makefile

@@ -181,12 +181,6 @@ CC_FLAGS_FTRACE := -pg
 ifdef CONFIG_MPROFILE_KERNEL
 CC_FLAGS_FTRACE += -mprofile-kernel
 endif
-# Work around gcc code-gen bugs with -pg / -fno-omit-frame-pointer in gcc <= 4.8
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44199
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52828
-ifndef CONFIG_CC_IS_CLANG
-CC_FLAGS_FTRACE	+= $(call cc-ifversion, -lt, 0409, -mno-sched-epilog)
-endif
 endif
 
 CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))