net/mlx5e: Use function to map aRFS into traffic type

For a better code reuse and readability, use the existing
function arfs_get_tt() to map arfs_type into mlx5e_traffic_types,
instead of duplicating the switch-case logic.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>