net/mlx5: E-switch, Reuse mlx5_eswitch_set_vport_mac

mlx5_eswitch_set_vport_mac() routine already does necessary checks which
are duplicated in implementation of
mlx5_devlink_port_function_hw_addr_set().

Hence, reuse mlx5_eswitch_set_vport_mac() and cut down the code.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>