When performing a channel switch flow for a managed interface, the
flow did not update the bandwidth of the AP station and the rate
scale algorithm. In case of a channel width downgrade, this would
result with the rate scale algorithm using a bandwidth that does not
match the interface channel configuration.

Fix this by updating the AP station bandwidth and rate scaling algorithm
before the actual channel change in case of a bandwidth downgrade, or
after the actual channel change in case of a bandwidth upgrade.
Signed-off-by: NIlan Peer <ilan.peer@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>