XXX: FH chanset should be calculated by FH hop pattern, but BayStack 650 AP
always specify chanset to fixed value 1. The previous code try to this
hack into awi driver, but it is insufficient because the chanset value
in awi driver may change while scan and it may be different from the
value in receiving beacon/probe-response. So we save encoded FH chanset
into channel in 802.11 common bss information for now.
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