media: v4l2-ctrls-api.c: add back dropped ctrl->is_new = 1

The patch adding support for dynamically allocated arrays accidentally
dropped the line setting ctrl->is_new to 1, thus new string values were
always ignored.

Fixes: fb582cb ("media: v4l2-ctrls: add support for dynamically allocated arrays.")
Reported-by: Alice Yuan <alice.yuan@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/v4l2-core/v4l2-ctrls-api.c

@@ -150,6 +150,7 @@ static int user_to_new(struct v4l2_ext_control *c, struct v4l2_ctrl *ctrl)
 			 * then return an error.
 			 */
 			if (strlen(ctrl->p_new.p_char) == ctrl->maximum && last)
+			ctrl->is_new = 1;
 				return -ERANGE;
 		}
 		return ret;