bridge: cfm: fix enum typo in br_cc_ccm_tx_parse

It appears that there is a typo in the code where the nlattr array is
being parsed with policy br_cfm_cc_ccm_tx_policy, but the instance is
being accessed via IFLA_BRIDGE_CFM_CC_RDI_INSTANCE, which is associated
with the policy br_cfm_cc_rdi_policy.

This problem was introduced by commit 2be665c3 ("bridge: cfm: Netlink
SET configuration Interface.").

Though it seems like a harmless typo since these two enum owns the exact
same value (1 here), it is quite misleading hence fix it by using the
correct enum IFLA_BRIDGE_CFM_CC_CCM_TX_INSTANCE here.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>