video: initial support for ADV7180

This is a an updated version of my previous patch.

Hans: I have updated the patch according to you feedback (almost). Thanks for the feedback btw.
* I left the state struct even though it only contains the subdev,
it's for the future when more functions are added in.
* I left the function for checking the norm, also for the future it's
for instance possible to get interrupts when the norm is changed, a schedule work or equal could then use this function too.

And yes, Mocean laboratories is the author while it's copyrighted to Intel.

--Richard