[RFC] EDID parser updates

[Adam Jackson]

Some cosmetic cleanups, and then some changes to add more modes than we
were before.  6 and 7 are the particularly touchy bits; I'd like a bit of
volunteer testing before landing it on drm-core-next, particularly on
HDMI monitors.  Note that this is mostly about doing more with things
other than your preferred mode, so be sure to check the mode list you get
from RANDR for changes and try all the new ones (if any).

- ajax