CHROMIUM: mwifiex: Clean up scan state on error

CHROMIUM: mwifiex: Clean up scan state on error

De-reference and deallocate scan state on failure.

Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Paul Stewart <pstew@chromium.org>
BUG=chrome-os-partner:15087
TEST=Reproduce enable/disable of WiFi quickly

Change-Id: I660200025abad5d9718c1fdb0bd7ce4ecbef503e
Reviewed-on: https://gerrit.chromium.org/gerrit/35480
Reviewed-by: Bing Zhao <bzhao@marvell.com>
Reviewed-by: Ryan Cairns <rtc@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>