net/mlx5: DR, Remove HW specific STE type from nic domain

Instead of using the HW specific STEv0 type, it is better to use
an enum to indicate if this is an RX or TX nic domain.
This means that now we will need to convert the nic domain type
to the corresponding STE type.

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