s390/bitops: fix inline assembly constraints

Fix inline assembly contraints for non atomic bitops functions.

This is broken since 2.6.34 987bcdac "[S390] use inline assembly
contraints available with gcc 3.3.3".

Reported-by: Andreas Krebbel <krebbel@linux.vnet.ibm.com>
Reported-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>