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

Track "NRIPS exposed to L1" via a governed feature flag instead of using
a dedicated bit/flag in vcpu_svm.

No functional change intended.

Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-9-seanjc@google.com


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