iwmc3200wifi: refuse to associate on unallowed channels

We need to make sure we don't associate with APs on unallowed
channels (according to regulatory setting). This could happen
when the channel is not specified (auto-select) within the
connection request. In this case we get the AP's channel until
the firmware indicates the association succeeded later. We need
to verify the associated channel. If the channel is disabled by
regulatory, we have to disassociate with the AP.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>