drm/i915: fix ILK+ infoframe support
Misc fixes based on tests with an infoframe analyzer:
- checksum *does* include header bytes
- DIP enable & AVI infoframe are tied together in hw, so disable both
and make sure AVI frames are enabled first
- use every vsync flag for SPD frames to avoid reserved value in
frequency field when enabling both AVI & SPD
Fixes https://bugs.freedesktop.org/show_bug.cgi?id=40281.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@kernel.org
Signed-off-by: Keith Packard <keithp@keithp.com>