s390/flags: use _BITUL macro

The defines that are used in entry.S have been partially converted to
use the _BITUL macro (setup.h). This patch converts the rest.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>