vga: fix build when fbdev is a module

This fixes the build breakage reported by Stephen in -next
when merging the drm-next tree.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/vga/vgaarb.c

@@ -137,6 +137,8 @@ struct pci_dev *vga_default_device(void)
 	return vga_default;
 }
 
+EXPORT_SYMBOL_GPL(vga_default_device);
+
 void vga_set_default_device(struct pci_dev *pdev)
 {
 	vga_default = pdev;

drivers/video/efifb.c

@@ -305,6 +305,8 @@ struct pci_dev *vga_default_device(void)
 	return default_vga;
 }
 
+EXPORT_SYMBOL_GPL(vga_default_device);
+
 void vga_set_default_device(struct pci_dev *pdev)
 {
 	default_vga = pdev;