f2fs: don't leak filename in f2fs_try_convert_inline_dir()

We need to call fscrypt_free_filename() to free the memory allocated by
fscrypt_setup_filename().

Fixes: b06af2aff28b ("f2fs: convert inline_dir early before starting rename")
Cc: <stable@vger.kernel.org> # v5.6+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>