x86/cpufeatures: Add HWP highest perf change feature flag

When CPUID[6].EAX[15] is set to 1, this CPU supports notification for
HWP (Hardware P-states) highest performance change.

Add a feature flag to check if the CPU supports HWP highest performance
change.

Signed-off-by: Srinivas Pandruvada <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: spandruvada

arch/x86/include/asm/cpufeatures.h

@@ -361,6 +361,7 @@
 #define X86_FEATURE_HWP_ACT_WINDOW	(14*32+ 9) /* HWP Activity Window */
 #define X86_FEATURE_HWP_EPP		(14*32+10) /* HWP Energy Perf. Preference */
 #define X86_FEATURE_HWP_PKG_REQ		(14*32+11) /* HWP Package Level Request */
+#define X86_FEATURE_HWP_HIGHEST_PERF_CHANGE (14*32+15) /* "" HWP Highest perf change */
 #define X86_FEATURE_HFI			(14*32+19) /* Hardware Feedback Interface */
 
 /* AMD SVM Feature Identification, CPUID level 0x8000000a (EDX), word 15 */