CHROMIUM: mwifiex: cancel pending scan commands if scan is already aborted

CHROMIUM: mwifiex: cancel pending scan commands if scan is already aborted

The scan could be aborted by cfg80211 core.c.
Driver should not send any pending scan commands to firmware.

Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Paul Stewart <pstew@chromium.org>
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.
Turn on driver debug and verify the pending scan commands are
cancelled after scan is aborted by cfg80211.

Change-Id: I8d27266bbda150d34ac442149030c8cfd4e663ab
Reviewed-on: https://gerrit.chromium.org/gerrit/35500
Reviewed-by: Ryan Cairns <rtc@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>