media: i2c: Add driver for RDACM21 camera module

The RDACM21 is a GMSL camera supporting 1280x1080 resolution images
developed by IMI based on an Omnivision OV10640 sensor, an Omnivision
OV490 ISP and a Maxim MAX9271 GMSL serializer.

The driver uses the max9271 library module, to maximize code reuse with
other camera module drivers using the same serializer, such as rdacm20.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>