iwlwifi 3945: secondary interface disallows association

[Andy Green <andy@warmcat.com>]

Hi folks -

I have pretty decent functionality on the 3945abg laptop with the Fedora
development kernel version of iwlwifi and WPA via wpa_supplicant.
Connections can stay up over a couple of days or more when I am staying
close to the AP.

However if I perform this action:

echo -n mon0 > /sys/class/ieee80211/phy0/add_iface

I immediately lose association and cannot reacquire it until I remove
the iwl3945 module and insert again.  I don't have to do anything with
the new interface, just create it.  I tried setting the channel and mode
of it, but that didn't help with reacquiring an association.

In contrast I can bring up other virtual interfaces okay on, eg, zd1211
without losing an existing association to the same WPA network.

-Andy