drm/dp: s/I2C_STATUS/I2C_WRITE_STATUS_UPDATE/

Rename the I2C_STATUS request to I2C_WRITE_STATUS_UPDATE to match the
spec.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
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>