pc-bios/s390-ccw: get LOADPARM stored in SCP Read Info

Obtain the loadparm value stored in SCP Read Info by performing
a SCLP Read Info request.

Rename sclp-ascii.c to sclp.c to reflect the changed scope of
the file.

Signed-off-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>