iwlwifi: mvm: Reflect GO channel switch in NoA

According to the spec, GO/AP should perform the channel switch just
before "beacon 0". However, since the exact timing isn't defined,
it may result in a sudden GO disappearance from the channel.
Prevent potential packet loss when performing the CS by scheduling
NoA time event and executing the channel switch flow when a notification
from fw is received.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>