Update top-level README to match the change to a "agl-refhw-h3"
feature in meta-agl that was integrated for Kooky Koi, and to
remove the note about HDMI issues, as they have been resolved.
Bug-AGL: SPEC-3708
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Ic3e398abd47b0a79c8f0cb5847ebca2018fb924c