virtio: Add module driver macro for virtio drivers.

Add helper macro for drivers that don't do anything
special in module init/exit.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/virtio.h

@@ -126,4 +126,13 @@ static inline struct virtio_driver *drv_to_virtio(struct device_driver *drv)
 
 int register_virtio_driver(struct virtio_driver *drv);
 void unregister_virtio_driver(struct virtio_driver *drv);
+
+/* module_virtio_driver() - Helper macro for drivers that don't do
+ * anything special in module init/exit.  This eliminates a lot of
+ * boilerplate.  Each module may only use this macro once, and
+ * calling it replaces module_init() and module_exit()
+ */
+#define module_virtio_driver(__virtio_driver) \
+	module_driver(__virtio_driver, register_virtio_driver, \
+			unregister_virtio_driver)
 #endif /* _LINUX_VIRTIO_H */