rds/ib: use system_wq instead of rds_ib_fmr_wq

With cmwq, there's no reason to use dedicated rds_ib_fmr_wq - it's not
in the memory reclaim path and the maximum number of concurrent work
items is bound by the number of devices.  Drop it and use system_wq
instead.  This rds_ib_fmr_init/exit() noops.  Both removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andy Grover <andy.grover@oracle.com>
diff --git a/net/rds/ib.c b/net/rds/ib.c
index 4123967..cce19f95 100644
--- a/net/rds/ib.c
+++ b/net/rds/ib.c
@@ -364,7 +364,6 @@
 	rds_ib_sysctl_exit();
 	rds_ib_recv_exit();
 	rds_trans_unregister(&rds_ib_transport);
-	rds_ib_fmr_exit();
 }
 
 struct rds_transport rds_ib_transport = {
@@ -400,13 +399,9 @@
 
 	INIT_LIST_HEAD(&rds_ib_devices);
 
-	ret = rds_ib_fmr_init();
-	if (ret)
-		goto out;
-
 	ret = ib_register_client(&rds_ib_client);
 	if (ret)
-		goto out_fmr_exit;
+		goto out;
 
 	ret = rds_ib_sysctl_init();
 	if (ret)
@@ -430,8 +425,6 @@
 	rds_ib_sysctl_exit();
 out_ibreg:
 	rds_ib_unregister_client();
-out_fmr_exit:
-	rds_ib_fmr_exit();
 out:
 	return ret;
 }