media: atomisp: don't store an unused sink data on a var

Fixes this Werror breakage:

drivers/staging/media/atomisp/pci/atomisp_ioctl.c: In function 'atomisp_streamon':
drivers/staging/media/atomisp/pci/atomisp_ioctl.c:1714:44: error: variable 'sink' set but not used [-Werror=unused-but-set-variable]
 1714 |                 struct v4l2_mbus_framefmt *sink;
      |                                            ^~~~
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/staging/media/atomisp/pci/atomisp_ioctl.c

@@ -1711,11 +1711,9 @@ static int atomisp_streamon(struct file *file, void *fh,
 
 start_delay_wq:
 	if (asd->continuous_mode->val) {
-		struct v4l2_mbus_framefmt *sink;
-
-		sink = atomisp_subdev_get_ffmt(&asd->subdev, NULL,
-					       V4L2_SUBDEV_FORMAT_ACTIVE,
-					       ATOMISP_SUBDEV_PAD_SINK);
+		atomisp_subdev_get_ffmt(&asd->subdev, NULL,
+				        V4L2_SUBDEV_FORMAT_ACTIVE,
+				        ATOMISP_SUBDEV_PAD_SINK);
 
 		reinit_completion(&asd->init_done);
 		asd->delayed_init = ATOMISP_DELAYED_INIT_QUEUED;