f2fs: stop issue discard if something wrong with f2fs

v4->v5: move data corruption check to __submit_discard_cmd, in order to
control discard io submitted more accurately, besides, increase async
thread wait time if data corruption detected.

This patch stop async thread and umount process to issue discard
if something wrong with f2fs, which is similar to fstrim.

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>