[media] V4L: add media bus configuration subdev operations

Add media bus configuration types and two subdev operations to get
supported mediabus configurations and to set a specific configuration.
Subdevs can support several configurations, e.g., they can send video data
on 1 or several lanes, can be configured to use a specific CSI-2 channel,
in such cases subdevice drivers return bitmasks with all respective bits
set. When a set-configuration operation is called, it has to specify a
non-ambiguous configuration.

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