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>

diff --cc drivers/gpu/drm/nouveau/Makefile
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/include/subdev/i2c.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/base.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nv04.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nv4e.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nv50.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nv94.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nvd0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/nve0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/pad.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/pad.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/padnv04.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/padnv94.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/priv.h
Simple merge