[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/NCR5380.c b/drivers/scsi/NCR5380.c
index 9a5629f..e7cd2fc 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -936,8 +936,7 @@
 {
 	struct NCR5380_hostdata *hostdata = (struct NCR5380_hostdata *) instance->hostdata;
 
-	cancel_delayed_work(&hostdata->coroutine);
-	flush_scheduled_work();
+	cancel_delayed_work_sync(&hostdata->coroutine);
 }
 
 /**