[SCSI] scsi_transport_sas: add support for transport layer retries (TLR)

The mpt2sas driver wants to use transport layer retries (TLR) so the
simplest thing to do seems to be to add the enabling flags and checks
to the SAS transport class, since they're a SAS specific protocol
feature.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/scsi/scsi_sas_internal.h b/drivers/scsi/scsi_sas_internal.h
index 998cb5b..6266a5d 100644
--- a/drivers/scsi/scsi_sas_internal.h
+++ b/drivers/scsi/scsi_sas_internal.h
@@ -5,7 +5,7 @@
 #define SAS_PHY_ATTRS		17
 #define SAS_PORT_ATTRS		1
 #define SAS_RPORT_ATTRS		7
-#define SAS_END_DEV_ATTRS	3
+#define SAS_END_DEV_ATTRS	5
 #define SAS_EXPANDER_ATTRS	7
 
 struct sas_internal {