drm/i915: Sort DEV_INFO_FOR_EACH_FLAG

Sort DEV_INFO_FOR_EACH_FLAG to alphabetical order (except is_*).

v2:
- Add comments in the hope of maintaining order (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1475664617-24541-1-git-send-email-joonas.lahtinen@linux.intel.com