When __v4l2_ctrl_modify_range() fails, no error return code of
imx274_s_frame_interval() is assigned.
To fix this bug, ret is assigned with the return valye of
__v4l2_ctrl_modify_range(), and then ret is checked.

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>