gma: Add Kaby Lake support

Including some weird Amber Lake Y parts that are treated like Kaby Lake
in Linux' i915.

Only differences to Skylake in the DDI output buffer tuning.

Change-Id: Ice05e07b016cebc7258a9790e38e079e63227a4b
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/28763
Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/common/hw-gfx-gma.ads b/common/hw-gfx-gma.ads
index 40382f8..b9c627b 100644
--- a/common/hw-gfx-gma.ads
+++ b/common/hw-gfx-gma.ads
@@ -43,7 +43,8 @@
       Haswell,
       Broadwell,
       Broxton,
-      Skylake);
+      Skylake,
+      Kabylake);
 
    type CPU_Variant is (Normal, ULT, ULX);