[S390] Don't use small stacks when lockdep is used.

The lock dependency validator adds a bunch of extra stack frames to
the stack, which can cause stack overflows. Especially seen on 31 bit
where the small stack is only 4k.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>