drm/nouveau: off by one in init_i2c_device_find()

dcb->i2c[] has DCB_MAX_NUM_I2C_ENTRIES entries.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>