Derive lvds_dual_channel from EDID timings.

Based on the info by Felix Held.

Change-Id: Iab84dd8a0e3c942da20a6e21db5510e4ad16cadd
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/11857
Tested-by: build bot (Jenkins)
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/include/edid.h

@@ -33,6 +33,7 @@ enum edid_modes {
 struct edid_mode {
 	const char *name;
 	unsigned int pixel_clock;
+	int lvds_dual_channel;
 	unsigned int refresh;
 	unsigned int ha;
 	unsigned int hbl;