gma pch lvds: Fully initialize port register

This very stale code only ever worked because it left old settings in-
tact (i.e. settings done by the Video BIOS). So initialize everything
needed for known LVDS displays to work.

TEST=none so far

Change-Id: If5dcc186ca1d4a07deb2ca78f018d613f5e029ad
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/17022
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/TODO b/TODO
index 7efa9e1..71b578a 100644
--- a/TODO
+++ b/TODO
@@ -2,4 +2,4 @@
 medium	DP	honor adjust requests also if training succeeded?
 unknown	DP	honor SINK_STATUS after training
 
-low	LVDS	sync polarity, 8bit colors, data format???
+low	LVDS	8bit colors, data format???