[S390] cmm: get rid of CMM_PROC config option

All distros have this option switched on, so lets get rid of at least
one of the tons of config options that are available.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>