s390/sclp: _sclp_wait_int(): retain full PSW mask

There's no reason to clear all PSW mask bits other than the addressing
mode bits. Just use the previous PSW mask as-is.

Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>