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>
1 file changed