net/mlx5: E-Switch, Use RoCE version 2 for loopback traffic

Could be port initializing eswitch doesn't support RoCE version 1
but all ports should support RoCE version 2.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>