x86, mce: don't set up mce sysdev devices with mce=off

Impact: bug fix, in this case the resume handler shouldn't run which
	avoids incorrectly reenabling machine checks on resume

When MCEs are completely disabled on the command line don't set
up the sysdev devices for them either.

Includes a comment fix from Thomas Gleixner.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/cpu/mcheck/mce_64.c

@@ -151,6 +151,8 @@ static void mce_panic(char *msg, struct mce *backup, unsigned long start)
 
 static int mce_available(struct cpuinfo_x86 *c)
 {
+	if (mce_dont_init)
+		return 0;
 	return cpu_has(c, X86_FEATURE_MCE) && cpu_has(c, X86_FEATURE_MCA);
 }
 
@@ -532,8 +534,7 @@ void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
 {
 	mce_cpu_quirks(c);
 
-	if (mce_dont_init ||
-	    !mce_available(c))
+	if (!mce_available(c))
 		return;
 
 	mce_init(NULL);
@@ -710,8 +711,7 @@ static int __init mcheck_disable(char *str)
 	return 1;
 }
 
-/* mce=off disables machine check. Note you can re-enable it later
-   using sysfs.
+/* mce=off disables machine check.
    mce=TOLERANCELEVEL (number, see above)
    mce=bootlog Log MCEs from before booting. Disabled by default on AMD.
    mce=nobootlog Don't log MCEs from before booting. */