media: i2c: Defer probe if not endpoint found

The ov8865 driver is one of those that can be connected to a CIO2
device by the cio2-bridge code. This means that the absence of an
endpoint for this device is not necessarily fatal, as one might be
built by the cio2-bridge when it probes. Return -EPROBE_DEFER if no
endpoint is found rather than a fatal error.

Signed-off-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>