media: i2c: ov9281: Fixup for recent kernel releases, and remove custom code

The Rockchip driver was based on a 4.4 kernel, and had several custom
Rockchip parts.

Update to 5.4 kernel APIs, with the relevant controls required by
libcamera, and remove custom Rockchip parts.

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