s390/smp: convert cpuhp_setup_state() return code to zero on success

cpuhp_setup_state() returns a state number on CPUHP_AP_ONLINE_DYN if
no error occurred. Therefore convert the return code to zero before
using it as exit code for s390_smp_init().
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/smp.c

@@ -1181,6 +1181,7 @@ static int __init s390_smp_init(void)
 
 	rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "s390/smp:online",
 			       smp_cpu_online, smp_cpu_pre_down);
+	rc = rc <= 0 ? rc : 0;
 out:
 	return rc;
 }