net: stmmac: selftests: Mark as fail when received VLAN ID != expected

When the VLAN ID does not match the expected one it means filter failed
in HW. Fix it.

Fixes: 94e18382 ("net: stmmac: selftests: Add selftest for VLAN TX Offload")
Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>