s390: fix 'novx' early parameter handling

Specifying the 'novx' kernel parameter always results in a warning:

Malformed early option 'novx'

The reason for this is that the novx early parameter handling function
always returns a non-zero value which means that an error occurred.
Fix this and return the correct zero value instead.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/early.c

@@ -420,7 +420,7 @@ static int __init disable_vector_extension(char *str)
 {
 	S390_lowcore.machine_flags &= ~MACHINE_FLAG_VX;
 	__ctl_clear_bit(0, 17);
-	return 1;
+	return 0;
 }
 early_param("novx", disable_vector_extension);