drm/i915/dsi: lose the loose 666 format name in favor of packed

The enum mipi_dsi_pixel_format defines MIPI_DSI_FMT_RGB666 for the
"loose" 24 bpp format and MIPI_DSI_FMT_RGB666_PACKED for the 18 bpp
format. We have this the other way round, defining a loose version for
24 bpp.

Follow suit with what's in enum mipi_dsi_pixel_format to avoid future
confusion. Rename

VID_MODE_FORMAT_RGB666 -> VID_MODE_FORMAT_RGB666_PACKED
VID_MODE_FORMAT_RGB666_LOOSE -> VID_MODE_FORMAT_RGB666

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458123700-16003-1-git-send-email-jani.nikula@intel.com