net/mlx5: E-Switch, set flow source for send to uplink rule

Set the flow source param to local vport for the uplink rep
send-to-vport rule.

This will comply with the recent changes in SW steering that
use the flow source as an indication for the rule type - rx or tx.

Since the uplink send-to-vport rule is forwarding traffic to the wire
it has to indicate that it is an sx rule and can't use the any port
value in the flow source.

Signed-off-by: Ariel Levkovich <lariel@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>