mlx5: Add arbitrary sg list support

Allocate proper context for arbitrary scatterlist registration
If ib_alloc_mr is called with IB_MR_MAP_ARB_SG, the driver
allocate a private klm list instead of a private page list.
Set the UMR wqe correctly when posting the fast registration.

Also, expose device cap IB_DEVICE_MAP_ARB_SG according to the
device id (until we have a FW bit that correctly exposes it).

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 55fa588..7e89a54 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -491,6 +491,8 @@
 		props->device_cap_flags |= IB_DEVICE_MEM_WINDOW |
 					   IB_DEVICE_MEM_WINDOW_TYPE_2B;
 		props->max_mw = 1 << MLX5_CAP_GEN(mdev, log_max_mkey);
+		/* We support 'Gappy' memory registration too */
+		props->device_cap_flags |= IB_DEVICE_SG_GAPS_REG;
 	}
 	props->device_cap_flags |= IB_DEVICE_MEM_MGT_EXTENSIONS;
 	if (MLX5_CAP_GEN(mdev, sho)) {