x86/cpu, kvm: Add support for CPUID_80000021_EAX

x86/cpu, kvm: Add support for CPUID_80000021_EAX

Add support for CPUID leaf 80000021, EAX. The majority of the features will be
used in the kernel and thus a separate leaf is appropriate.

Include KVM's reverse_cpuid entry because features are used by VM guests, too.

  [ bp: Massage commit message. ]

Signed-off-by: Kim Phillips <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Acked-by: Sean Christopherson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]