IB/cma: Add default RoCE TOS to CMA configfs

Add new entry to the RDMA-CM configfs that allows users
to select default TOS for RDMA-CM QPs.

This is useful for users that want to control the TOS for legacy
applications without changing their code.

Application that sets the TOS explicitly using the rdma_set_option
API will continue to work as expected, meaning overriding the configfs
value.

CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

Documentation/ABI/testing/configfs-rdma_cm

@@ -20,3 +20,11 @@ Description: 	RDMA-CM based connections from HCA <hca> at port <port-num>
 		will be initiated with this RoCE type as default.
 		The possible RoCE types are either "IB/RoCE v1" or "RoCE v2".
 		This parameter has RW access.
+
+What: 		/config/rdma_cm/<hca>/ports/<port-num>/default_roce_tos
+Date: 		February 7, 2017
+KernelVersion:  4.11.0
+Description: 	RDMA-CM QPs from HCA <hca> at port <port-num>
+		will be created with this TOS as default.
+		This can be overridden by using the rdma_set_option API.
+		The possible RoCE TOS values are 0-255.