gma: Add Setup_Default_FB()

Add new public procedure Setup_Default_FB() to configure a framebuffer
in stolen memory. The optional parameter `Clear` tells it to clear the
configured framebuffer.

Also remove Setup_Default_GTT() from the public interface.

Change-Id: I6ece4f56bbd34126ef34f0107d5ccdbde8a007ac
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20603
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/common/hw-gfx-framebuffer_filler.adb b/common/hw-gfx-framebuffer_filler.adb
index e55e9be..250d903 100644
--- a/common/hw-gfx-framebuffer_filler.adb
+++ b/common/hw-gfx-framebuffer_filler.adb
@@ -12,6 +12,7 @@
 -- GNU General Public License for more details.
 --
 
+with HW.Config;
 with HW.MMIO_Range;
 pragma Elaborate_All (HW.MMIO_Range);
 
@@ -27,6 +28,10 @@
    is
       Line_Start : Int32 := 0;
    begin
+      if not HW.Config.Dynamic_MMIO then
+         return;
+      end if;
+
       FB.Set_Base_Address (Linear_FB);
       for Line in 0 .. Framebuffer.Height - 1 loop
          pragma Loop_Invariant (Line_Start = Line * Framebuffer.Stride);