need to adjust inline symlink padding logic for rhel9

[allisonkarlitskaya]

[ 44.746985] erofs: (device loop0): erofs_fill_symlink: inline data cross block boundary @ nid 3966
ls: cannot access '/etc/systemd/system/local-fs.target.wants/tmp.mount': Structure needs cleaning

fwiw:

>>> 3966 * 32
126912
>>> 126912 % 4096
4032
>>> 4096 - 4032
64

which is to say that the extended inode ends exactly at the block boundary and the inline data is in the next page. That's valid for all data on newer kernels and for non-symlinks on older kernels, but the kernel on rhel9 (5.14.0) doesn't like it for symlinks.

We should probably just adjust this for all inline files to make sure the last bytes of the inode+xattr data fall into the same block as the start of the inline data...