x86, mce: fix "mce" boot option handling for CONFIG_X86_NEW_MCE

"mce argument mce ignored. Please use /sys" message shouldn't
be printed when using "mce" boot option.
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Reviewed-by: NAndi Kleen <andi@firstfloor.org>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/cpu/mcheck/mce.c

@@ -1549,8 +1549,10 @@ static struct miscdevice mce_log_device = {
  */
 static int __init mcheck_enable(char *str)
 {
-	if (*str == 0)
+	if (*str == 0) {
 		enable_p5_mce();
+		return 1;
+	}
 	if (*str == '=')
 		str++;
 	if (!strcmp(str, "off"))