vgaarb: a NULL bridge is acceptable for root devices.

I assumed all PCI buses had a bridge, but playing with qemu recently, I
discovered vgaarb bug where it wasn't detecting both devices shared a bridge
at the root level.

Don't check for NULL, if two buses have a NULL bridge, assume they share the
root bus.
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/vga/vgaarb.c

@@ -465,7 +465,6 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
 	while (new_bus) {
 		new_bridge = new_bus->self;
 
-		if (new_bridge) {
 		/* go through list of devices already registered */
 		list_for_each_entry(same_bridge_vgadev, &vga_list, list) {
 			bus = same_bridge_vgadev->pdev->bus;
@@ -491,7 +490,6 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
 				bus = bus->parent;
 			}
 		}
-		}
 		new_bus = new_bus->parent;
 	}
 }