xen/blkback: Add module alias for autoloading

Add xen-backend:vbd module alias to the xen-blkback module. This allows
automatic loading of the module.
Signed-off-by: Bastian Blank <waldi@debian.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkback/blkback.c

@@ -826,3 +826,4 @@ static int __init xen_blkif_init(void)
 module_init(xen_blkif_init);
 
 MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("xen-backend:vbd");