s390: introduce compile time check for empty .bss section

Introduce compile time check for files which should avoid using .bss
section, because of the following reasons:
- .bss section has not been zeroed yet,
- initrd has not been moved to a safe location and could be overlapping
with .bss section.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>