KVM: arm64: vgic-its: Return -ENXIO to invalid KVM_DEV_ARM_VGIC_GRP_CTRL attrs

A preliminary version of a hack to invoke unmap_all_vpes() from an ioctl
didn't work very well. We eventually determined this was because we were
invoking it on the wrong file descriptor, but not getting an error.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/bbbddd56135399baf699bc46ffb6e7f08d9f8c9f.camel@infradead.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: dwmw2

arch/arm64/kvm/vgic/vgic-its.c

@@ -2694,6 +2694,9 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
 	case KVM_DEV_ARM_ITS_RESTORE_TABLES:
 		ret = abi->restore_tables(its);
 		break;
+	default:
+		ret = -ENXIO;
+		break;
 	}
 
 	mutex_unlock(&its->its_lock);