iwlwifi: mvm: offload channel switch timing to FW

iwlwifi: mvm: offload channel switch timing to FW

Since FW is now in charge of timing the channel switch, there is no need
to send the add/modify/remove time event command to fw with every (e)CSA
element.
However, the driver needs to cancel the channel switch if the CS start
notification arrives and it does not know about an ongoing channel switch.

Signed-off-by: Nathan Errera <nathan.errera@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220128153013.ac3af0ff22c7.Ie87c62047b71b93b12aa80b5dc5391b4798dbe97@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>