[ACPI] generic Hot Key support

See Documentation/acpi-hotkey.txt

Use cmdline "acpi_specific_hotkey" to enable
legacy platform specific drivers.

http://bugzilla.kernel.org/show_bug.cgi?id=3887

Signed-off-by: Luming Yu <luming.yu@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/asus_acpi.c

@@ -1204,6 +1204,10 @@ static int __init asus_acpi_init(void)
 	if (acpi_disabled)
 		return -ENODEV;
 
+	if (!acpi_specific_hotkey_enabled){
+		printk(KERN_ERR "Using generic hotkey driver\n");
+		return -ENODEV;	
+	}
 	asus_proc_dir = proc_mkdir(PROC_ASUS, acpi_root_dir);
 	if (!asus_proc_dir) {
 		printk(KERN_ERR "Asus ACPI: Unable to create /proc entry\n");