s390/ipl: rename diagnose enums

Rename DIAG308_IPL and DIAG308_DUMP to DIAG308_LOAD_CLEAR and
DIAG308_LOAD_NORMAL_DUMP to better reflect the associated IPL
functions.

Suggested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>