gma: Add a HW.PCI.Dev for dynamic MMIO setup

Remove `MMIO_Base` option from Initialize() and try to derive it
using libhwbase' PCI mechanism instead.

Change-Id: Iacd4d098954bb96c1c6b40fdfb2636191d9517c7
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20600
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/gfxtest/hw-gfx-gma-gfx_test.adb b/gfxtest/hw-gfx-gma-gfx_test.adb
index b7060ec..ad396fd 100644
--- a/gfxtest/hw-gfx-gma-gfx_test.adb
+++ b/gfxtest/hw-gfx-gma-gfx_test.adb
@@ -165,15 +165,8 @@
       end if;
       Screen.Set_Base_Address (Res_Addr);
 
-      Dev.Map (Res_Addr, PCI.Res0);
-      if Res_Addr = 0 then
-         Debug.Put_Line ("Failed to map PCI resource0.");
-         return;
-      end if;
-
       GMA.Initialize
-        (MMIO_Base   => Res_Addr,
-         Clean_State => True,
+        (Clean_State => True,
          Success     => Initialized);
 
       if Initialized then