media: rcar-csi2: Update start procedure for V4H

Prepare for adding D-PHY support to the driver by first updating the
generic startup procedure that covers both C-PHY and D-PHY operations.
The starting procedure where updated in later versions of the datasheet.

Most of the configuration is only documented as tables of magic values
in the documentation. Each step is however marked with a T<n> marker,
inject these markers in the comments to make it easier to map driver to
documentation.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250612175904.1126717-4-niklas.soderlund+renesas@ragnatech.se


Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>