Fix v4l2 template caps probe for MTK MT21 format

gst-inspect-1.0 v4l2convert returns incorrect template
caps as MT21 template omits the format field. Fall through
to correct this.

Change-Id: I5f421ff2bbd267a2c28dc92c1d1ca0e98a44a7c9
diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index 0fefbfb..df17fb3 100644
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -1512,8 +1512,6 @@
       structure = gst_structure_new_empty ("video/x-pn-realvideo");
       break;
     case V4L2_PIX_FMT_MT21:
-      structure = gst_structure_new_empty ("video/x-raw");
-      break;
     case V4L2_PIX_FMT_GREY:    /*  8  Greyscale     */
     case V4L2_PIX_FMT_Y16:
     case V4L2_PIX_FMT_Y16_BE: