net/mlx5: DR, Set STEv0 ICMP flex parser dynamically

Set the flex parser ID dynamicly for ICMP instead of relying
on hardcoded values.

Signed-off-by: Muhammad Sammar <muhammads@nvidia.com>
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>