f2fs: convert inline data for direct I/O & FI_NO_PREALLOC

In FI_NO_PREALLOC cases, direct I/O path may allocate blocks for an
inode but keep its inline data flag. This inconsistency may trigger
vfs clear_inode nrpages bug_on when evicting the inode. We should
convert inline data first in this case.

Signed-off-by: Weichao Guo <guoweichao@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>