fs: jfs: (trivial) Fix typo in dbInitTree function

While trying to fix the jfs UBSAN problem reported in syzkaller,
(https://syzkaller.appspot.com/bug?id=01abadbd6ae6a08b1f1987aa61554c6b3ac19ff2

)

I found the typo in the comment of dbInitTree function and fix it.

Signed-off-by: Wonguk Lee <wonguk.lee1023@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>