fix warning in fs/dlm/netlink.c

this warning:

  fs/dlm/netlink.c: In function ‘dlm_timeout_warn’:
  fs/dlm/netlink.c:131: warning: ‘send_skb’ may be used uninitialized in this function

triggers because GCC does not recognize the (correct) error flow
between prepare_data() and send_skb.

Annotate it.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

fs/dlm/netlink.c

@@ -127,8 +127,8 @@ static void fill_data(struct dlm_lock_data *data, struct dlm_lkb *lkb)
 
 void dlm_timeout_warn(struct dlm_lkb *lkb)
 {
+	struct sk_buff *uninitialized_var(send_skb);
 	struct dlm_lock_data *data;
-	struct sk_buff *send_skb;
 	size_t size;
 	int rv;