gma skl: Disable DDI clocks on reset path

After reset DPLL_CTRL2 is initialized to 0. Which means some clock
disable bits are not set and might cause some hassle later. Set them
and close the related TODO.

Change-Id: I1a470dff55e317e8119906b3e397f6f2314abcbd
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20648
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 b3818a3..99a1276 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -408,8 +408,10 @@
          Registers.Clear_Fences;
       else
          -- According to PRMs, VGA plane is the only thing
-         -- that's enabled by default after reset.
+         -- that's enabled by default after reset...
          Display_Controller.Legacy_VGA_Off;
+         -- ... along with some DDI port bits since Skylake.
+         Connectors.Post_Reset_Off;
       end if;
 
       -------------------- Now restart from a clean state ---------------------