SUNRPC: Allow caller of rpc_sleep_on() to select priority levels

Currently, the caller has to change the value of task->tk_priority if
it wants to select on which priority level the task will sleep.

This patch allows the caller to select a priority level at sleep time
rather than always using task->tk_priority.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index fe2d8e6..e775689 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -227,6 +227,10 @@
 void		rpc_destroy_wait_queue(struct rpc_wait_queue *);
 void		rpc_sleep_on(struct rpc_wait_queue *, struct rpc_task *,
 					rpc_action action);
+void		rpc_sleep_on_priority(struct rpc_wait_queue *,
+					struct rpc_task *,
+					rpc_action action,
+					int priority);
 void		rpc_wake_up_queued_task(struct rpc_wait_queue *,
 					struct rpc_task *);
 void		rpc_wake_up(struct rpc_wait_queue *);