libhdmi: Let EDID scan for FullHD resolutions if the HDMI sysfs allows it

The revalidation clauses had a resolution ceiling on 720p, and only allowed
EDID values below that. If the user has the 1080p bootscript, let it scan
for higher values, too.

Change-Id: Ieb3cc8fa101b3a10bd343f443cead578407ab70e