block: handle blk_pm_resume_request() requests in blk_execute_rq_nowait()

For blk_pm_resume_request() requests (which are used only by IDE subsystem currently) the queue is stopped so we need to call ->request_fn explicitly.

Thanks to:
- Rafael for reporting/bisecting the bug
- Borislav/Rafael for testing the fix

This is a preparation for converting IDE to use blk_execute_rq().

---
goes before "ide: convert ide_do_drive_cmd path to use blk_execute_rq" patch in IDE tree

 block/blk-exec.c |    3 +++
 1 file changed, 3 insertions(+)

Index: b/block/blk-exec.c
===================================================================
@@ -58,6 +58,9 @@ void blk_execute_rq_nowait(struct reques
 	spin_lock_irq(q->queue_lock);
 	__elv_add_request(q, rq, where, 1);
 	__generic_unplug_device(q);
+	/* the queue is stopped so it won't be plugged+unplugged */
+	if (blk_pm_resume_request(rq))
+		q->request_fn(q);
 	spin_unlock_irq(q->queue_lock);
 }
 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);