net/mlx5: DR, Remove unneeded rx_decap_l3 function for STEv1

Remove the dr_ste_v1_set_rx_decap_l3 function that was
replaced by another function - fixing a rebase error.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>