jfs: fix array-index-out-of-bounds in dbFindLeaf

Currently while searching for dmtree_t for sufficient free blocks there
is an array out of bounds while getting element in tp->dm_stree. To add
the required check for out of bound we first need to determine the type
of dmtree. Thus added an extra parameter to dbFindLeaf so that the type
of tree can be determined and the required check can be applied.

Reported-by:  <syzbot+aea1ad91e854d0a83e04@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=aea1ad91e854d0a83e04
Signed-off-by: Manas Ghandat <ghandatmanas@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>