s390/cmma: cleanup inline assemblies

Cleanup cmma related inline assemblies:
- consolidate inline assemblies
- use symbolic names
- add same white space where missing
- add braces to for-loops which contain a multi-line statement

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>