x86/cpufeatures: Hide AMD-specific speculation flags

Hide the AMD_{IBRS,IBPB,STIBP} flag from /proc/cpuinfo.  This was done
upstream as part of commit e7c587da "x86/speculation: Use
synthetic bits for IBRS/IBPB/STIBP".  That commit has already been
backported but this part was omitted.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/include/asm/cpufeatures.h

@@ -271,9 +271,9 @@
 /* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
 #define X86_FEATURE_CLZERO	(13*32+0) /* CLZERO instruction */
 #define X86_FEATURE_IRPERF	(13*32+1) /* Instructions Retired Count */
-#define X86_FEATURE_AMD_IBPB	(13*32+12) /* Indirect Branch Prediction Barrier */
-#define X86_FEATURE_AMD_IBRS	(13*32+14) /* Indirect Branch Restricted Speculation */
-#define X86_FEATURE_AMD_STIBP	(13*32+15) /* Single Thread Indirect Branch Predictors */
+#define X86_FEATURE_AMD_IBPB	(13*32+12) /* "" Indirect Branch Prediction Barrier */
+#define X86_FEATURE_AMD_IBRS	(13*32+14) /* "" Indirect Branch Restricted Speculation */
+#define X86_FEATURE_AMD_STIBP	(13*32+15) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_VIRT_SSBD	(13*32+25) /* Virtualized Speculative Store Bypass Disable */
 
 /* Thermal and Power Management Leaf, CPUID level 0x00000006 (eax), word 14 */