staging: wfx: rewrite wfx_hw_scan()

staging: wfx: rewrite wfx_hw_scan()

Scan requests from mac80211 must be splitted in a few hardware requests
(it is necessary to split channels with active scan and channels with
passive scan). Current code schedules a work_struct for each hardware
request and one delayed_work to handle scan timeout.

It is far simpler to run send all the hardware requests synchronously
and replace delayed_work with a simple wait_for_completion_timeout().

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191217161318.31402-51-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>