drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes

A address-only I2C_WRITE can't be replied with a short i2c ack, but I
suppose it could be replied with an i2c defer. So the code should be
prepared for an address-only I2C_WRITE_STATUS_UPDATE.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: "Terje Bergström" <tbergstrom@nvidia.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>