s390/mm,fault: have balanced braces, remove unnecessary blanks

Remove unnecessary braces and also blanks after casts.
Add braces to have balanced braces where missing.

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>