KVM: nSVM: Use KVM-governed feature framework to track "Pause Filter enabled"

Track "Pause Filtering is exposed to L1" via governed feature flags
instead of using dedicated bits/flags in vcpu_svm.

No functional change intended.

Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-13-seanjc@google.com


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