iwlwifi: mvm: continue (with error) CSA on GO time event failure

If, on a GO, the CSA time event fails to be scheduled, continue the
flow towards mac80211's state machine so it doesn't get stuck, but
report an error later on the post switch which will cause mac80211
to tear down the operation. This ensures nothing gets stuck due to
the scheduling failure.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>