drm/i915: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE

When we get an i2c defer or short ack for i2c-over-aux write we need
to switch to WRITE_STATUS_UPDATE to poll for the completion of the
original request.

i915 doesn't try to interpret wht request type apart from separating
reads from writes, and so we should be able to treat this the same as
a normal i2c write.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>