net/mlx5: Change define name for 0x100 lkey value

Change define of 0x100 lkey value from MLX5_INVALID_LKEY to be
MLX5_TERMINATE_SCATTER_LIST_LKEY as 0x100 is the value of
terminate_scatter_list_mkey.

Link: https://lore.kernel.org/r/3a116dc3fbae4cb6b76a63d27d418830b06ade0c.1673960981.git.leon@kernel.org
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>