media: i2c: ds90ub960: Add RX port iteration support

media: i2c: ds90ub960: Add RX port iteration support

The driver does a lot of iteration over the RX ports with for loops. In
most cases the driver will skip unused RX ports. Also, in the future
patches the FPD-Link IV support will be refreshed with TI's latest init
sequences which involves a lot of additional iterations over the RX
ports, often only for FPD-Link IV ports.

To make the iteration simpler and to make it clearer what we're
iterating over (all or only-active, all or only-fpd4), add macros and
support functions for iterating the RX ports. Use the macros in the
driver, replacing the for loops.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>