f2fs: apply write hints to select the type of segment for direct write

When blocks are allocated for direct write, select the type of
segment using the kiocb hint. But if an inode has FI_NO_ALLOC,
use the inode hint.

Signed-off-by: Hyunchul Lee <cheol.lee@lge.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>