OvmfPkg/QemuVideoDxe: Add SubClass field to QEMU_VIDEO_CARD

Then check for PCI_CLASS_DISPLAY_VGA using the new field.
This allows to enable/disable non-vga display classes per
card entry.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/QemuVideoDxe/Qemu.h

@@ -96,6 +96,7 @@ typedef enum {
 } QEMU_VIDEO_VARIANT;
 
 typedef struct {
+  UINT8                                 SubClass;
   UINT16                                VendorId;
   UINT16                                DeviceId;
   QEMU_VIDEO_VARIANT                    Variant;