gma: Provide `Global` contracts for public procedures

We have to enforce a contract on Power_Up_VGA(), as it has no effect
on older hardware generations.

Change-Id: I13af0d90ff738e1eea5f8992718e00a6a09c4705
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/26866
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: Nico Huber <nico.h@gmx.de>
diff --git a/common/hw-gfx-framebuffer_filler.adb b/common/hw-gfx-framebuffer_filler.adb
index 250d903..29c7da6 100644
--- a/common/hw-gfx-framebuffer_filler.adb
+++ b/common/hw-gfx-framebuffer_filler.adb
@@ -17,6 +17,8 @@
 pragma Elaborate_All (HW.MMIO_Range);
 
 package body HW.GFX.Framebuffer_Filler
+with
+   Refined_State => (State => FB.State, Base_Address => FB.Base_Address)
 is
 
    type FB_Index is new Natural range