drm/i915: put the IOSF port defines in numerical order

Make it easier to spot duplicates.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/a89f10d2d1954ac1b9a278534cb5209973354caa.1454582914.git.jani.nikula@intel.com