net/mlx5: fix multiple definitions of mlx5_lag_mpesw_init / mlx5_lag_mpesw_cleanup

static inline is needed in the header.

Fixes: 94db3317 ("net/mlx5: Support multiport eswitch mode")
Acked-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20220518183022.2034373-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>