media: ti: j721e-csi2rx: Fix NULL vs IS_ERR() bug in ti_csi2rx_request_max_ppc()

media: ti: j721e-csi2rx: Fix NULL vs IS_ERR() bug in ti_csi2rx_request_max_ppc()

The media_entity_remote_source_pad_unique() function never returns NULL,
it returns error pointers.  Change this check from a NULL check to an
IS_ERR() check.

Fixes: 31f91c5224cd ("media: ti: j721e-csi2rx: Support multiple pixels per clock")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Jai Luthra <jai.luthra@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>