KVM: SVM: fix up incorrect backport

When I backported 52918ed5 ("KVM: SVM: Override default MMIO mask if
memory encryption is enabled") to 4.19 (which resulted in commit
a4e761c9 ("KVM: SVM: Override default MMIO mask if memory encryption
is enabled")), I messed up the call to kvm_mmu_set_mmio_spte_mask()

Fix that here now.
Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/svm.c

@@ -1336,7 +1336,7 @@ static __init void svm_adjust_mmio_mask(void)
 	 */
 	mask = (mask_bit < 52) ? rsvd_bits(mask_bit, 51) | PT_PRESENT_MASK : 0;
 
-	kvm_mmu_set_mmio_spte_mask(mask, PT_WRITABLE_MASK | PT_USER_MASK);
+	kvm_mmu_set_mmio_spte_mask(mask, mask);
 }
 
 static __init int svm_hardware_setup(void)