virtio: Make VIRTIO_NET depend on NETDEVICES

As VIRTIO_NET is the symbol for enabling network devices, make this
depend on NETDEVICES

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 852f673..1de6886 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -56,7 +56,7 @@
 
 config VIRTIO_NET
 	bool "virtio net driver"
-	depends on VIRTIO
+	depends on VIRTIO && NETDEVICES
 	help
 	  This is the virtual net driver for virtio. It can be used with
 	  QEMU based targets.