staging/atomisp: fix returnvar.cocci warnings

drivers/staging/media/atomisp/pci/atomisp2/atomisp_subdev.c:161:5-8: Unneeded variable: "ret". Return "0" on line 163

 Remove unneeded variable used to store return value.

Generated by: scripts/coccinelle/misc/returnvar.cocci
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/media/atomisp/pci/atomisp2/atomisp_subdev.c

@@ -158,9 +158,7 @@ uint16_t atomisp_subdev_source_pad(struct video_device * vdev)
 static long isp_subdev_ioctl(struct v4l2_subdev *sd,
 	unsigned int cmd, void *arg)
 {
-	int ret = 0;
-
-	return ret;
+	return 0;
 }
 
 /*