KVM: SVM: Add Virtual VMLOAD VMSAVE feature definition

Define a new cpufeature definition for Virtual VMLOAD VMSAVE.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>