gcc incorrectly removes initialization of register 0 in dasd diag
inline assembly. Use different register to work around this compiler
bug.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NPeter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>