media: stm32-dcmi: use int type to store negative error codes

media: stm32-dcmi: use int type to store negative error codes

Change "ret" from unsigned int to int type in dcmi_framesizes_init()
and dcmi_graph_notify_bound() to store negative error codes or zero
returned by v4l2_subdev_call() and media_create_pad_link() - this
better aligns with the coding standards and maintains code consistency.

No effect on runtime.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>