KVM: nSVM: Use KVM-governed feature framework to track "LBRv enabled"
Track "LBR virtualization exposed to L1" via a governed feature flag
instead of using a dedicated bit/flag in vcpu_svm.
Note, checking KVM's capabilities instead of the "lbrv" param means that
the code isn't strictly equivalent, as lbrv_enabled could have been set
if nested=false where as that the governed feature cannot. But that's a
glorified nop as the feature/flag is consumed only by paths that are
gated by nSVM being enabled.
Link: https://lore.kernel.org/r/20230815203653.519297-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>