xen: add virtual network device driver

The network device frontend driver allows the kernel to access network
devices exported exported by a virtual machine containing a physical
network device driver.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Acked-by: Jeff Garzik <jeff@garzik.org>
Cc: Ian Pratt <ian.pratt@xensource.com>
Cc: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>
Cc: netdev@vger.kernel.org
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index eb41676..0e286ab 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -127,6 +127,8 @@
 obj-$(CONFIG_SLIP) += slip.o
 obj-$(CONFIG_SLHC) += slhc.o
 
+obj-$(CONFIG_XEN_NETDEV_FRONTEND) += xen-netfront.o
+
 obj-$(CONFIG_DUMMY) += dummy.o
 obj-$(CONFIG_IFB) += ifb.o
 obj-$(CONFIG_MACVLAN) += macvlan.o