wl1271: Clear probe-request template after scan

Clear the probe-request template on the firmware after scan. Unless
cleared, the firmware can independently send probe requests to the AP
and interfere with the mac80211 logic.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>