gma broxton: Add final glue

Add new configuration flags for Broxton and hook up its DDI_Phy
implementation in the shared Haswell DDI code. Haswell and Skylake
get DDI_Phy stubs.

Tested (in Linux userspace) on ASRock J3455-ITX which exposes the
following ports:
  o VGA through an active eDP to VGA converter chip
  o HDMI 2.0 through an active DP to HDMI converter chip
  o DVI-D connected to the SoC

Change-Id: If72b228c6a4c45487261e6e7435d281ec2d97f38
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/18426
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index 77ce2aa..21b123d 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -381,10 +381,12 @@
       -------------------- Now restart from a clean state ---------------------
       Power_And_Clocks.Initialize;
 
-      Registers.Unset_And_Set_Mask
-        (Register    => Registers.PCH_RAWCLK_FREQ,
-         Mask_Unset  => PCH_RAWCLK_FREQ_MASK,
-         Mask_Set    => PCH_RAWCLK_FREQ (Config.Default_RawClk_Freq));
+      if Config.Has_PCH then
+         Registers.Unset_And_Set_Mask
+           (Register    => Registers.PCH_RAWCLK_FREQ,
+            Mask_Unset  => PCH_RAWCLK_FREQ_MASK,
+            Mask_Set    => PCH_RAWCLK_FREQ (Config.Default_RawClk_Freq));
+      end if;
 
       Initialized := True;