V4L/DVB (11610): soc-camera: simplify register access routines in multiple sensor drivers

Register access routines only need the I2C client, not the soc-camera device
context.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>