media: staging: media: imx: imx7-media-csi: Move misc init out of probe()

There is a chunk of miscellaneous initializations related to the CSI
subdev and media pads directly in the probe function. Move them into the
imx7_csi_media_init() function to clean up the probe function.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>