f2fs: correct statistic of APP_DIRECT_IO/APP_DIRECT_READ_IO

Miss to update APP_DIRECT_IO/APP_DIRECT_READ_IO when receiving async DIO.
For example: fio -filename=/data/test.0 -bs=1m -ioengine=libaio -direct=1
		-name=fill -size=10m -numjobs=1 -iodepth=32 -rw=write

Signed-off-by: Jack Qiu <jack.qiu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>