target/i386: ignore ARCH_CAPABILITIES features in user mode emulation

ARCH_CAPABILITIES is only accessible through a read-only MSR, so it has
no impact on any user-mode operation (user-mode cannot read the MSR).
So do not bother printing warnings about it in user mode emulation.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -1069,6 +1069,13 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .msr = {
             .index = MSR_IA32_ARCH_CAPABILITIES,
         },
+        /*
+         * FEAT_ARCH_CAPABILITIES only affects a read-only MSR, which
+         * cannot be read from user mode.  Therefore, it has no impact
+         > on any user-mode operation, and warnings about unsupported
+         * features do not matter.
+         */
+        .tcg_features = ~0U,
     },
     [FEAT_CORE_CAPABILITY] = {
         .type = MSR_FEATURE_WORD,