mac80211: properly drop the connection in case of invalid CSA IE

In case the frequency is invalid, ieee80211_parse_ch_switch_ie
will fail and we may not even reach the check in
ieee80211_sta_process_chanswitch. Drop the connection
in case ieee80211_parse_ch_switch_ie failed, but still
take into account the CSA mode to remember not to send
a deauth frame in case if it is forbidden to.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210409123755.34712ef96a0a.I75d7ad7f1d654e8b0aa01cd7189ff00a510512b3@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>