[media] media: mt9m111: make a standalone v4l2 subdevice

Remove the soc_camera adherence. Mostly the change removes the power
manipulation provided by soc_camera, and instead :
 - powers on the sensor when the s_power control is activated
 - powers on the sensor in initial probe
 - enables and disables the MCLK provided to it in power on/off

This patch also drops support for inverters on synchronisation and clock
lines. It is assumed, if any board ever needs such inverters, support
for them can be added in the future

Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>