net/mlx4_en: avoid indirect call in TX completion

Commit 9ecc2d86 ("net/mlx4_en: add xdp forwarding and data write support")
brought another indirect call in fast path.

Use INDIRECT_CALL_2() helper to avoid the cost of the indirect call
when/if CONFIG_RETPOLINE=y

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Willem de Bruijn <willemb@google.com>
Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>