media: camss: csiphy: Split to hardware dependent and independent parts

This will allow to add support for different hardware.

Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
[hans.verkuil@cisco.com: remove trailing empty line]
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>