irq_poll: fold irq_poll_sched_prep into irq_poll_sched

There is no good reason to keep them apart, and this makes using the API
a bit simpler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 88af879..43a3370 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -21,13 +21,17 @@
  *
  * Description:
  *     Add this irq_poll structure to the pending poll list and trigger the
- *     raise of the blk iopoll softirq. The driver must already have gotten a
- *     successful return from irq_poll_sched_prep() before calling this.
+ *     raise of the blk iopoll softirq.
  **/
 void irq_poll_sched(struct irq_poll *iop)
 {
 	unsigned long flags;
 
+	if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
+		return;
+	if (!test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
+		return;
+
 	local_irq_save(flags);
 	list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
 	__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
@@ -58,7 +62,7 @@
  * Description:
  *     If a driver consumes less than the assigned budget in its run of the
  *     iopoll handler, it'll end the polled mode by calling this function. The
- *     iopoll handler will not be invoked again before irq_poll_sched_prep()
+ *     iopoll handler will not be invoked again before irq_poll_sched()
  *     is called.
  **/
 void irq_poll_complete(struct irq_poll *iop)