nl80211: Fix AP-scan-in-STA-mode error path behavior
If a second scan trigger attempt fails in STA mode, the error path was
supposed to restore the old mode that was in use before changing to STA
mode. However, wpa_driver_nl80211_set_mode() changes drv->nlmode on
success, so the recovery path needs to use the saved old_mode value
instead.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>