x86/svm: use nsvm_efer_svm_enabled() to check guest's EFER.SVME

There's a macro for this, might improve readability a bit & save a bit of space.

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/hvm/svm/nestedsvm.c

@@ -1616,7 +1616,7 @@ void svm_nested_features_on_efer_update(struct vcpu *v)
      * Need state for transfering the nested gif status so only write on
      * the hvm_vcpu EFER.SVME changing.
      */
-    if ( v->arch.hvm.guest_efer & EFER_SVME )
+    if ( nsvm_efer_svm_enabled(v) )
     {
         if ( !vmcb->virt_ext.fields.vloadsave_enable &&
              paging_mode_hap(v->domain) &&

xen/arch/x86/hvm/svm/svm.c

@@ -253,7 +253,7 @@ static void cf_check svm_update_guest_efer(struct vcpu *v)
     vmcb_set_efer(vmcb, guest_efer);
 
     ASSERT(nestedhvm_enabled(v->domain) ||
-           !(v->arch.hvm.guest_efer & EFER_SVME));
+           !nsvm_efer_svm_enabled(v));
 
     if ( nestedhvm_enabled(v->domain) )
         svm_nested_features_on_efer_update(v);