KVM: nSVM: Use common GPA helper to check for illegal CR3

Replace an open coded check for an invalid CR3 with its equivalent
helper.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210204000117.3303214-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -345,7 +345,7 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
 static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
 			       bool nested_npt)
 {
-	if (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63))
+	if (kvm_vcpu_is_illegal_gpa(vcpu, cr3))
 		return -EINVAL;
 
 	if (!nested_npt && is_pae_paging(vcpu) &&