CHROMIUM: mwifiex: Abort scan when interface is down

CHROMIUM: mwifiex: Abort scan when interface is down

When the interface is marked down, scans should be aborted,
otherwise we risk memory leaks and code paths that may cause
a crash.

Signed-off-by: Paul Stewart <pstew@chromium.org>
BUG=chrome-os-partner:15390
TEST="iw mlan0 scan trigger; ifconfig mlan0 down"

Change-Id: I7a9010ce3086a19fbcd143db60dee27290f1e78b
Reviewed-on: https://gerrit.chromium.org/gerrit/36151
Reviewed-by: Bing Zhao <bzhao@marvell.com>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>