gma broxton: Start off with power domains and CDClk

It's close to the respective code for Skylake but still different
enough for a separate implementation. We start with a default CDClk
of 288MHz which is enough for resolutions up to 2560x1600.

Change-Id: I44364191236f421b2b89c9a019a50713f7c20525
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/18243
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.ads b/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.ads
index 7c5a647..87f5d07 100644
--- a/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.ads
+++ b/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.ads
@@ -15,6 +15,7 @@
 private package HW.GFX.GMA.Power_And_Clocks_Haswell is
 
    procedure PSR_Off;
+   procedure GT_Mailbox_Write (MBox : Word32; Value : Word32);
 
    procedure Pre_All_Off;
    procedure Post_All_Off is null;