erofs-utils: lib: fix compressed packed inodes

erofs-utils: lib: fix compressed packed inodes

Commit 2fdbd28 fixed uncompressed packed inodes by not always writing
compressed data, but it broke compressed packed inodes because now
uncompressed file data is always written after the compressed data.

The new error handling always rewinds with lseek and falls through to
write_uncompressed_file_from_fd, regardless of whether the compressed
data was written successfully (ret = 0) or not (ret = -ENOSPC). This
can result in corrupted files.

Fix it by simplifying the error handling to better match the old code.

Fixes: 2fdbd28 ("erofs-utils: lib: fix uncompressed packed inode")
Co-authored-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Danny Lin <danny@orbstack.dev>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240923051759.7563-2-danny@orbstack.dev
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>