[SCSI] libsas: add mutex for SMP task execution

SAS does not tag SMP requests, and at least one lldd (isci) does not permit
more than one in-flight request at a time.

[jejb: fix sas_init_dev tab issues while we're at it]
Signed-off-by: Jeff Skirvin <jeffrey.d.skirvin@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index f388ba5..18704a2e 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -153,6 +153,8 @@
 
 	struct ex_phy *ex_phy;
 	struct sas_port *parent_port;
+
+	struct mutex cmd_mutex;
 };
 
 /* ---------- SATA device ---------- */