s390/cio: Use BITS_TO_LONGS() instead of __BITOPS_WORDS()

Use BITS_TO_LONGS() instead of __BITOPS_WORDS() that is considered
to be private macro in asm/bitops.h for s390.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>