s390/sclp_cpi: remove sclp_cpi module in favor of sysfs interface

Since commit c05ffc4f

 ("[S390] sclp: sysfs interface for
SCLP cpi"), which was made 2008 the user can specify a system
and sysplex name through the /sys/firmware/cpi interface.  In
addition to sysplex and system name, the user can also override
the system type and system version.

Because the syfs interface is easier to use and allows the
settings to be updated, the sclp_cpi module becomes obsolete
and can be removed.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>