media: ti-vpe: cal: Implement subdev ops for CAMERARX

Implement subdev operations for the CAMERARX. They will be used to
replace calls to custom CAMERARX functions in the V4L2 video device
code, and will be exposed to userspace.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>