media/bcm2835-unicam: Add support for configuration via MC API

Adds Media Controller API support for more complex pipelines.
libcamera is about to switch to using this mechanism for configuring
sensors.

This can be enabled by either a module parameter, or device tree.

Various functions have been moved to group video-centric and
mc-centric functions together.

Based on a similar conversion done to ti-vpe.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>