staging: wfx: drop wdev->output_power

mac80211 and the device are both able to control tx power per vif. But,
the current code retrieve tx power from wfx_config(). So, it does not
allow to setup the tx power independently for each vif. Driver just has
to rely on bss_conf->txpower to get the correct information.

In add, it is no more necessary to protect access to wdev->output_power
with scan_lock.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200115135338.14374-15-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>