drm/nouveau/i2c: switch to instanced constructor

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/i2c/gk110-: disable hw-initiated dpcd reads

RM does this around transactions, and it seemed to help while debugging
AUXCH issues on GA102.

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

drm/nouveau/i2c/gk110: split out from i2c/gk104

No functional changes here yet.

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