s390/sclp: convert to use sysfs_emit()

Use sysfs_emit() for all sclp sysfs show functions, which is the
current standard way to generate output strings.

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>