drbd: Split off on-the-wire protocol definitions

Keep the protocol definitions separate from the kernel code; they are useful in
their own right.

Signed-off-by: Andreas Gruenbacher <agruen@linbit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index a861648..bd515e7 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -44,6 +44,7 @@
 #include <linux/string.h>
 #include <linux/scatterlist.h>
 #include "drbd_int.h"
+#include "drbd_protocol.h"
 #include "drbd_req.h"
 
 #include "drbd_vli.h"