media: sun6i-csi: Move register configuration to capture

Continue moving things over to capture in tidy helpers.
Also take the occasion to remove the config struct, which is
unwelcome redundancy and use the capture helpers instead.

The code is only adapted to reflect the removal of the config
structure. No functional change intended.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>