drm: Ensure universal_planes is set for atomic

Atomic doesn't really work without universal planes anyway. But make
sure that evil userspace doesn't pull the kernel over the table
because we didn't consider a cornercase that just doesn't make sense,
just for safety.

v2: Just force ->universal_planes to the same value to avoid imposing
restrictions on userspace.

Cc: Rob Clark <robdclark@gmail.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/drm_ioctl.c

@@ -355,6 +355,7 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 		if (req->value > 1)
 			return -EINVAL;
 		file_priv->atomic = req->value;
+		file_priv->universal_planes = req->value;
 		break;
 	default:
 		return -EINVAL;