s390/stacktrace: remove call_on_stack_noreturn()

There is no user left of call_on_stack_noreturn() - remove it.

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>