mb/asrock/b85m_pro4: Make VGA work on Linux

Currently, having libgfxinit try to enable VGA will result in a hang.
On the Asrock B85M Pro4, DDI E (VGA) was not being enabled in coreboot,
so it did not hang. However, this renders Linux's i915 driver unable to
use VGA at all. In absence of monitors with digital inputs, this is bad.

To work around this problem, mark DDI E as enabled, and comment out VGA
from gma-mainboard.ads for the time being. This allows one to use a VGA
monitor, even if it only works after Linux drivers have taken over.

Change-Id: Idd6a9e8515a1065ad3c6ddf136896fef9f0fa732
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42099
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Michael Niewöhner

src/mainboard/asrock/b85m_pro4/devicetree.cb

@@ -1,5 +1,8 @@
 chip northbridge/intel/haswell
 
+	# This mainboard has VGA
+	register "gpu_ddi_e_connected" = "1"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/haswell
 			register "c1_acpower" = "1"

src/mainboard/asrock/b85m_pro4/gma-mainboard.ads

@@ -11,7 +11,8 @@ private package GMA.Mainboard is
    ports : constant Port_List :=
      (HDMI1,  -- DVI-D
       HDMI3,  -- HDMI
-      Analog, -- VGA
+      -- FIXME: Haswell VGA support in libgfxinit is broken
+      -- Analog, -- VGA
       others => Disabled);
 
 end GMA.Mainboard;