[PATCH] erofs-utils: fsck: fix directory loop tracking

[Nithurshen]

Hi Xiang,

This patch LGTM.

I tested the fix by compiling fsck with a debug trace and running
it against an image with a nested directory structure. I verified
that the recursion stack now correctly pushes the current directory's
NID (inode.nid) instead of inheriting the parent's NID, successfully
fixing the loop tracking logic.

Reviewed-by: Nithurshen <nithurshen.dev at gmail.com>
Tested-by: Nithurshen <nithurshen.dev at gmail.com>