selftests: forwarding: vxlan_bridge_1d: Fix vxlan ecn decapsulate value

The ECN bit defines ECT(1) = 1, ECT(0) = 2. So inner 0x02 + outer 0x01
should be inner ECT(0) + outer ECT(1). Based on the description of
__INET_ECN_decapsulate, the final decapsulate value should be
ECT(1). So fix the test expect value to 0x01.

Before the fix:
TEST: VXLAN: ECN decap: 01/02->0x02                                 [FAIL]
        Expected to capture 10 packets, got 0.

After the fix:
TEST: VXLAN: ECN decap: 01/02->0x01                                 [ OK ]

Fixes: a0b61f3d

 ("selftests: forwarding: vxlan_bridge_1d: Add an ECN decap test")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>