KVM: selftests: Add x86 properties for Intel PMU in processor.h

Add x86 properties for Intel PMU so that tests don't have to manually
retrieve the correct CPUID leaf+register, and so that the resulting code
is self-documenting.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Link: https://lore.kernel.org/r/20230810090945.16053-2-cloudliang@tencent.com


Signed-off-by: Sean Christopherson <seanjc@google.com>