ncsi_channel_is_tx() determines whether a given channel should be
used for Tx or not. However, when reconfiguring the channel by
handling a Configuration Required AEN, there is a misjudgment that
the channel Tx has already been enabled, which results in the Enable
Channel Network Tx command not being sent.

Clear the channel Tx enable flag before reconfiguring the channel to
avoid the misjudgment.

Fixes: 8d951a75 ("net/ncsi: Configure multi-package, multi-channel modes with failover")
Signed-off-by: Cosmo Chou <chou.cosmo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>