media: sun6i-csi: Add support for MIPI CSI-2 to the bridge code

Introduce MIPI CSI-2 support to the bridge with a new port, source
and hardware configuration helper.

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>