QemuVideo: stdvga mmio bar support

The qemu standard vga has a MMIO bar in qemu 1.3+.
Use it if available.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13969 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/QemuVideoDxe/Qemu.h

@@ -90,6 +90,7 @@ typedef enum {
   QEMU_VIDEO_CIRRUS_5430 = 1,
   QEMU_VIDEO_CIRRUS_5446,
   QEMU_VIDEO_BOCHS,
+  QEMU_VIDEO_BOCHS_MMIO,
 } QEMU_VIDEO_VARIANT;
 
 typedef struct {
@@ -478,6 +479,13 @@ BochsRead (
   UINT16                   Reg
   );
 
+VOID
+VgaOutb (
+  QEMU_VIDEO_PRIVATE_DATA  *Private,
+  UINTN                    Reg,
+  UINT8                    Data
+  );
+
 EFI_STATUS
 QemuVideoCirrusModeSetup (
   QEMU_VIDEO_PRIVATE_DATA  *Private