[media] V4L: mt9m111: propagate higher level abstraction down in functions

It is more convenient to propagate the higher level abstraction - the
struct mt9m111 object into functions and then retrieve a pointer to
the i2c client, if needed, than to do the reverse.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>