rockchip: Make gpiod pin control work and add gpio-ranges

[Matthijs Kooijman]

The first patch fixes pin config (e.g. bias) done by userspace via the
gpiod interface, which was not implemented for all rockchip boards.

The second patch is just because I was messing with this code already
and had a test setup ready. It makes gpio-ranges explicit for the rk3308
instead of relying on the (possibly fragile) legacy workaround in
gpio-rockchip to add them automatically.

I think the first patch might be a good candidate to backport to the
stable releases, since it makes a userspace interface functional that
currently silently fails. However, it is not a clear bugfix and I am not
super familiar with the rules for -stable, so if you think this is not
appropriate, feel free to drop the stable Cc from the patch when merging.

Both patches were tested on a rock pi s with a rk3308.