x86, i8259: Only register sysdev if we have a real 8259 PIC

My platform makes use of the null_legacy_pic choice and oopses when doing
a shutdown as the shutdown code goes through all the registered sysdevs
and calls their shutdown method which in my case poke on a non-existing
i8259.  Imho the i8259 specific sysdev should only be registered if the
i8259 is actually there.

Do not register the sysdev function when the null_legacy_pic is used so
that the i8259 resume, suspend and shutdown functions are not called.

Signed-off-by: Adam Lackorzynski <adam@os.inf.tu-dresden.de>
LKML-Reference: <201007202218.o6KMIJ3m020955@imap1.linux-foundation.org>
Cc: Jacob Pan <jacob.jun.pan@intel.com>
Cc: <stable@kernel.org> 2.6.34
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/i8259.c

@@ -276,16 +276,6 @@ static struct sys_device device_i8259A = {
 	.cls	= &i8259_sysdev_class,
 };
 
-static int __init i8259A_init_sysfs(void)
-{
-	int error = sysdev_class_register(&i8259_sysdev_class);
-	if (!error)
-		error = sysdev_register(&device_i8259A);
-	return error;
-}
-
-device_initcall(i8259A_init_sysfs);
-
 static void mask_8259A(void)
 {
 	unsigned long flags;
@@ -407,3 +397,18 @@ struct legacy_pic default_legacy_pic = {
 };
 
 struct legacy_pic *legacy_pic = &default_legacy_pic;
+
+static int __init i8259A_init_sysfs(void)
+{
+	int error;
+
+	if (legacy_pic != &default_legacy_pic)
+		return 0;
+
+	error = sysdev_class_register(&i8259_sysdev_class);
+	if (!error)
+		error = sysdev_register(&device_i8259A);
+	return error;
+}
+
+device_initcall(i8259A_init_sysfs);