KVM: x86: Avoid double CPUID lookup when updating MWAIT at runtime

KVM: x86: Avoid double CPUID lookup when updating MWAIT at runtime

Move the handling of X86_FEATURE_MWAIT during CPUID runtime updates to
utilize the lookup done for other CPUID.0x1 features.

No functional change intended.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-46-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>