net/mlx5: Avoid setting unused var when modifying vport node GUID

GCC complains on unused-but-set-variable, clean this up.

Fixes: 23898c76

 ('net/mlx5: E-Switch, Modify node guid on vf set MAC')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>