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/drivers/intel/gma/i915.h

@@ -288,7 +288,6 @@ u32 gtt_read(u32 reg);
 struct i915_gpu_controller_info
 {
 	int use_spread_spectrum_clock;
-	int lvds_dual_channel;
 	int link_frequency_270_mhz;
 	int lvds_num_lanes;
 	u32 backlight;