loader: before falling back to default, also use EDID standard timings
As we got EDID information, it may be the gfx adapter does not support the EDID suggested preferred resolution. The current code will fall back to default (800x600), if we can not use the preferred resolution.
We should also consult standard timings list to see if we can find "second best" resolution, and only then fall to default.
Testing done: tested with 2K Dell monitor; the hosts GFX does not support 2k resolution, but from standard timings list, it did pick next best option.