xen: Add xenbus device driver

Access to xenbus is currently handled via xenfs. This adds a device
driver for xenbus and makes xenfs use this code.

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>
diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
index 8dca685..a2ea363 100644
--- a/drivers/xen/xenbus/Makefile
+++ b/drivers/xen/xenbus/Makefile
@@ -1,4 +1,5 @@
 obj-y	+= xenbus.o
+obj-y	+= xenbus_dev_frontend.o
 
 xenbus-objs =
 xenbus-objs += xenbus_client.o