media: ov772x: make set_fmt() and s_frame_interval() return -EBUSY while streaming

media: ov772x: make set_fmt() and s_frame_interval() return -EBUSY while streaming

The ov772x driver is going to offer a V4L2 sub-device interface, so
changing the output data format and the frame interval on this sub-device
can be made anytime.  However, these requests are preferred to fail while
the video stream on the device is active.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>