s390/ioasm: use symbolic names for asm operands

Change remaining inline assemblies to also use symbolic names for
operands, use "Q" constraint when possible, and use "+" modifier so
that an operand needs to be specified only once.

Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>