IB/mlx5: Initialize mlx5_ib_qp signature-related members

If user requested signature enable we initialize relevant mlx5_ib_qp
members.  We mark the qp as sig_enable and we increase the effective
SQ size, but still limit the user max_send_wr to original size
computed.  We also allow the create_qp routine to accept sig_enable
create flag.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/include/linux/mlx5/qp.h b/include/linux/mlx5/qp.h
index d51eff7..152756e 100644
--- a/include/linux/mlx5/qp.h
+++ b/include/linux/mlx5/qp.h
@@ -37,6 +37,7 @@
 #include <linux/mlx5/driver.h>
 
 #define MLX5_INVALID_LKEY	0x100
+#define MLX5_SIG_WQE_SIZE	(MLX5_SEND_WQE_BB * 5)
 
 enum mlx5_qp_optpar {
 	MLX5_QP_OPTPAR_ALT_ADDR_PATH		= 1 << 0,