xen: remove DEFINE_XENBUS_DRIVER() macro

The DEFINE_XENBUS_DRIVER() macro looks a bit weird and causes sparse
errors.

Replace the uses with standard structure definitions instead.  This is
similar to pci and usb device registration.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
index 2064b45..441b44e 100644
--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -367,12 +367,13 @@
 };
 MODULE_ALIAS("xen:vtpm");
 
-static DEFINE_XENBUS_DRIVER(tpmfront, ,
-		.probe = tpmfront_probe,
-		.remove = tpmfront_remove,
-		.resume = tpmfront_resume,
-		.otherend_changed = backend_changed,
-	);
+static struct xenbus_driver tpmfront_driver = {
+	.ids = tpmfront_ids,
+	.probe = tpmfront_probe,
+	.remove = tpmfront_remove,
+	.resume = tpmfront_resume,
+	.otherend_changed = backend_changed,
+};
 
 static int __init xen_tpmfront_init(void)
 {