drm/i915/pch: Use minimal number of FDI lanes (v2)

This should be a small power savings. Tested on Lenovo T410 (Ironlake), LVDS
VGA and DisplayPort, up to 1920x1200R.

v2: Add Sandybridge support, fix obvious math error.

Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 8a64c15..1ee4717 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -152,6 +152,7 @@
 	bool lowfreq_avail;
 	struct intel_overlay *overlay;
 	struct intel_unpin_work *unpin_work;
+	int fdi_lanes;
 };
 
 #define to_intel_crtc(x) container_of(x, struct intel_crtc, base)