[media] solo6x10: add control framework

Note that the MOTION_THRESHOLD functionality has been temporarily reduced:
only the global threshold can be set, not the per-block. This will be
addressed in a later patch: controls are not the proper way to do this.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>