iwlwifi: mvm: handle CCA-EXT delay firmware notification

If there are frequent CCA delays due to the extension channel
as detected by the firmware, and we're on 2.4 GHz, then handle
this by disconnecting (with a reconnect hint).

When we disconnect, we'll also update our capabilities to use
only 20 MHz on the next connection (if it's on 2.4 GHz) as to
avoid the use of the extension channel that has too much noise.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210117130510.4de9c363b0b5.I709b7e6f73a7537c53f22d7418927691259de8a8@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>