gma: Add a flag to use GMCH transcoder registers

Change-Id: Ic9bff918bdcab3c5c55316cb6de1a8a8bf1c6430
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/25406
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/common/hw-gfx-gma-config.ads.template b/common/hw-gfx-gma-config.ads.template
index b38201e..a0f3eed 100644
--- a/common/hw-gfx-gma-config.ads.template
+++ b/common/hw-gfx-gma-config.ads.template
@@ -57,6 +57,7 @@
    Has_PF_Pipe_Select      : constant Boolean := CPU in Ivybridge .. Haswell;
    VGA_Plane_Workaround    : constant Boolean := CPU = Ivybridge;
    Has_GMCH_VGACNTRL       : constant Boolean := false;
+   Has_GMCH_DP_Transcoder  : constant Boolean := false;
 
    ----- Panel power: -----
    Has_PP_Write_Protection : constant Boolean := CPU <= Ivybridge;