media: imx: imx7-mipi-csis: Centralize initialization of pad formats

Pad formats for the active configuration are manually initialized in
mipi_csis_subdev_init(), while pad formats for the TRY configurations
are initialized by the subdev .init_cfg() operation. This creates a risk
of the two configurations not being synchronized. Fix it by initializing
formats in the .init_cfg() operation only, and calling it from
mipi_csis_subdev_init().

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>