media: imx: imx-mipi-csis: Fix active format initialization on source pad

Commit 5c0701a0 ("media: imx: csis: Store pads format separately")
broke initialization of the active format on the source pad, as it
forgot to update the .init_cfg() handler. Fix it.

Fixes: 5c0701a0 ("media: imx: csis: Store pads format separately")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>