Net driver using virtio

The network driver uses two virtqueues: one for input packets and one
for output packets.  This has nice locking properties (ie. we don't do
any for recv vs send).

TODO:
	1) Big packets.
	2) Multi-client devices (maybe separate driver?).
	3) Resolve freeing of old xmit skbs (Christian Borntraeger)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: netdev@vger.kernel.org
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index e5208f2..b101588 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -344,6 +344,7 @@
 unifdef-y += videodev2.h
 unifdef-y += videodev.h
 unifdef-y += virtio_config.h
+unifdef-y += virtio_net.h
 unifdef-y += wait.h
 unifdef-y += wanrouter.h
 unifdef-y += watchdog.h