media: ipu6: Obtain remote pad using media_pad_remote_pad_unique()

media: ipu6: Obtain remote pad using media_pad_remote_pad_unique()

There's no reason to use media_entity_remote_source_pad_unique() as we
know our pads. Use media_pad_remote_pad_unique() instead.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Bingbu Cao <bingbu.cao@intel.com>
Tested-by: Mehdi Djait <mehdi.djait@linux.intel.com> # Dell XPS 9315
Reviewed-by: Mehdi Djait <mehdi.djait@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>