dlm: fix plock dev_write return value

The return value on writes to the plock device should be
the number of bytes written.  It was returning 0 instead
when an nfs lock callback was involved.

Reported-by: Nathan Straz <nstraz@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
index d6d6e37..78878c5 100644
--- a/fs/dlm/plock.c
+++ b/fs/dlm/plock.c
@@ -379,7 +379,7 @@
 		struct plock_xop *xop;
 		xop = (struct plock_xop *)op;
 		if (xop->callback)
-			count = dlm_plock_callback(op);
+			dlm_plock_callback(op);
 		else
 			wake_up(&recv_wq);
 	} else