[SCSI] remove flush_scheduled_work() usages

Simple conversions to drop flush_scheduled_work() usages in
drivers/scsi.  More involved ones will be done in separate patches.

* NCR5380, megaraid_sas: cancel_delayed_work() +
  flush_scheduled_work() -> cancel_delayed_work_sync().

* mpt2sas_scsih: drop unnecessary flush_scheduled_work().

* arcmsr_hba, ipr, pmcraid: flush the used work explicitly instead of
  using flush_scheduled_work().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
index 5d6d07b..e7c9b41 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -4242,9 +4242,8 @@
 	/* cancel the delayed work if this work still in queue */
 	if (instance->ev != NULL) {
 		struct megasas_aen_event *ev = instance->ev;
-		cancel_delayed_work(
+		cancel_delayed_work_sync(
 			(struct delayed_work *)&ev->hotplug_work);
-		flush_scheduled_work();
 		instance->ev = NULL;
 	}
 
@@ -4417,9 +4416,8 @@
 	/* cancel the delayed work if this work still in queue*/
 	if (instance->ev != NULL) {
 		struct megasas_aen_event *ev = instance->ev;
-		cancel_delayed_work(
+		cancel_delayed_work_sync(
 			(struct delayed_work *)&ev->hotplug_work);
-		flush_scheduled_work();
 		instance->ev = NULL;
 	}