drm/nouveau/i2c: introduce locking at a per-port level

There's also provisions to allow a pad to be locked with a specific
routing, for an indefinite period of time.  This will be used in
future patches.

The G94+ pad driver will now also power-down pads when not required.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
14 files changed