{net,IB}/mlx5: QP/XRCD commands via mlx5 ifc

Remove old representation of manually created QP/XRCD commands layout
amd use mlx5_ifc canonical structures and defines.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>