workqueue: use mod_delayed_work() instead of __cancel + queue

Now that mod_delayed_work() is safe to call from IRQ handlers,
__cancel_delayed_work() followed by queue_delayed_work() can be
replaced with mod_delayed_work().

Most conversions are straight-forward except for the following.

* net/core/link_watch.c: linkwatch_schedule_work() was doing a quite
  elaborate dancing around its delayed_work.  Collapse it such that
  linkwatch_work is queued for immediate execution if LW_URGENT and
  existing timer is kept otherwise.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> 
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index a7d6347..55a5bc0 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -672,7 +672,6 @@
 
 	if (drive == current_reqD)
 		drive = current_drive;
-	__cancel_delayed_work(&fd_timeout);
 
 	if (drive < 0 || drive >= N_DRIVE) {
 		delay = 20UL * HZ;
@@ -680,7 +679,7 @@
 	} else
 		delay = UDP->timeout;
 
-	queue_delayed_work(floppy_wq, &fd_timeout, delay);
+	mod_delayed_work(floppy_wq, &fd_timeout, delay);
 	if (UDP->flags & FD_DEBUG)
 		DPRINT("reschedule timeout %s\n", message);
 	timeout_message = message;