[S390] incorrect reipl nss name.

/sys/firmware/reipl/nss/name contains the nss name when defsys or
savesys command has been executed. If the defsys or savesys command
fails the kernel_nss_name has to be cleared since a reipl on that
nss name won't be possible.
Signed-off-by: NHongjie Yang <hongjie@us.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/early.c

@@ -88,13 +88,17 @@ static noinline __init void create_kernel_nss(void)
 
 	__cpcmd(defsys_cmd, NULL, 0, &response);
 
-	if (response != 0)
+	if (response != 0) {
+		kernel_nss_name[0] = '\0';
 		return;
+	}
 
 	__cpcmd(savesys_cmd, NULL, 0, &response);
 
-	if (response != strlen(savesys_cmd))
+	if (response != strlen(savesys_cmd)) {
+		kernel_nss_name[0] = '\0';
 		return;
+	}
 
 	ipl_flags = IPL_NSS_VALID;
 }