f2fs: remove the unnecessary check in f2fs_xattr_fiemap

Whehter or not error occurs, checking "err == 1" is unnecessary
in f2fs_xattr_fiemap(), and just remove it here.

Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>