wl12xx: fix roaming

The wl12xx device normally drops all frames coming from BSSID
it is not joined with.

This behavior is configured today by the wl12xx driver in response
to a handful of ieee80211_bss_change and ieee80211_conf_changed
notification flags, such as BSS_CHANGED_ASSOC, BSS_CHANGED_BSSID,
IEEE80211_CONF_CHANGE_IDLE, etc..

This breaks when we roam to a new BSSID, where authentication frames
are sent before any BSS_CHANGED/CONF_CHANGED flags are received.
When this happens the hardware silently drops the authentication
responses, and the roaming fails.

Ideally this aggressive filtering behavior of the device should be disabled
upon a notification from mac80211. Such notification will take place
after multi-channel support will be added: mac80211 will likely send a
remain-on-channel notification to drivers when entering sensitive
states (like authentication), otherwise the firmware might jump to
different channels (to serve a different role).

Until those notifications materialize, disable the hw BSSID filter
when authentication requests are sent, so roaming would work.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>