wl1271: Change supported channel order for a more optimal scan

The mac80211 inserts channels into a scan request in the same order the driver
registers them. Use this fact to optimize scan by ordering the channels so
that adjacent channels don't get scanned consecutively.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>