CHROMIUM: mwifiex: do not call cfg80211_scan_done if scan is already aborted

CHROMIUM: mwifiex: do not call cfg80211_scan_done if scan is already aborted

The scan could be aborted by cfg80211 core.c:

if (WARN_ON(rdev->scan_req && rdev->scan_req->wdev == wdev)) {
        rdev->scan_req->aborted = true;
        ___cfg80211_scan_done(rdev, true);
}

Driver shouldn't call cfg80211_scan_done in this case, otherwise
it triggers a "Unable to handle kernel paging request at ..."

BUG=chrome-os-partner:15087
TEST=On Wi-Fi Network Settings, enable Wi-Fi and connect to AP,
then disable Wi-Fi. Repeat above test multiple time.

Change-Id: Ib054d27369ade4d0889880be3d77be0eb6513822
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Paul Stewart <pstew@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/35479
Reviewed-by: Ryan Cairns <rtc@chromium.org>