s390/kexec: change return value of machine_kexec_prepare

Returning -ENOSYS on kexec_load() is a bad idea since user space cannot
tell if the system call is not implmented or if it failed.
Use -EOPNOTSUPP in case somebody tries a kexec_load on a NSS image based
kernel instead.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/machine_kexec.c

@@ -159,7 +159,7 @@ int machine_kexec_prepare(struct kimage *image)
 
 	/* Can't replace kernel image since it is read-only. */
 	if (ipl_flags & IPL_NSS_VALID)
-		return -ENOSYS;
+		return -EOPNOTSUPP;
 
 	if (image->type == KEXEC_TYPE_CRASH)
 		return machine_kexec_prepare_kdump();