fuser: restore functionality by fixing fsid type

Use types from sys/stat.h for the filesystem and inode numbers for extra
safety.

PR: 259504
Reported by: Markus Wild <freebsd-bugs@virtualtec.ch>
MFC after: 1 week

(cherry picked from commit e18fbe6f19ed106f035c7d2aaeade6eb55cc0b5a)