media: i2c: Add driver for ST VD55G1 camera sensor

The VD55G1 is a monochrome global shutter camera with a 804x704 maximum
resolution with RAW8 and RAW10 bytes per pixel.
The driver supports :
- Auto exposure from the sensor, or manual exposure mode
- HDR subtraction mode, allowing edge detection and background removal
- Auto exposure cold start, using configuration values from last stream
to start the next one
- LED GPIOs for illumination
- Most standard camera sensor features (hblank, vblank, test patterns,
again, dgain, hflip, vflip, auto exposure bias, etc.)
Add driver source code to MAINTAINERS file.

Signed-off-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>