wl1271: Add trigger to net_device oper_state to change BT coex priority

Add a trigger to net_device changes to monitor for oper_state changes in order
to be able to inform the firmware when association is fully complete (including
the EAP negotiation.)

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>