[rfc] drm/edid: add support for displayid timings

[Dave Airlie]

It appears that Dell 5K monitors hide some mode timings
in the displayid block, this set of patches fixes up a few
bits of displayid support, then add support for extracting
the type 1 detailed timings that the Dell monitors use.

The first two patches are missing signoff but I've asked
for Tomas to provide them.

This at least gets the modelines into the modelist.

Dave.