staging: wfx: use ieee80211_beacon_loss() provided by mac80211

staging: wfx: use ieee80211_beacon_loss() provided by mac80211

The firmware is able to filter beacons and send a notification if one or
multiple beacons are not received. Note that it send this notification
only once. Only if it receive beacons gain, it send a new notification.

Currently, the driver handle the connection loss itself (see
wfx_cqm_bssloss_sm()). It send null frames and watch the answers.

This patch fixes all this mess:
  - settle firmware to send a notification on the first beacon loss
  - call ieee80211_beacon_loss() and let mac80211 handle all the process
  - since we do have notification for each beacon loss, add a period
    task that call ieee80211_beacon_loss() until we receive "REGAIN"
    notification.

Thus, we can drop the ugly wfx_cqm_bssloss_sm() and
wfx_bss_params_work().

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200420160311.57323-3-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>