ACS: Fix VHT80 segment picking

ACS: Fix VHT80 segment picking

For example, the previous implementation considered [44, 48, 52, 56] to
be a valid VHT80 channel -- which it is not. This resulted in, e.g.,
failure to start CAC when channels on overlapped segments included DFS
channels.

Add a check similar to the HT40 one to prevent that. The check is
performed this way as the ACS implementation assumes the primary channel
to be the first channel in a given segment.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>