media: ov2659: fix unbalanced mutex_lock/unlock

Avoid returning with mutex locked.

Fixes: fa8cb644 ("[media] ov2659: Don't depend on subdev API")

Cc: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/ov2659.c

@@ -1132,7 +1132,7 @@ static int ov2659_set_fmt(struct v4l2_subdev *sd,
 		mf = v4l2_subdev_get_try_format(sd, cfg, fmt->pad);
 		*mf = fmt->format;
 #else
-		return -ENOTTY;
+		ret = -ENOTTY;
 #endif
 	} else {
 		s64 val;