[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>
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index ceecc56..fa7f434 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -123,6 +123,15 @@
 	  Note that this is an ref. implementation only.  It may or may not work
 	  for your integrated video device.
 
+config ACPI_HOTKEY
+	tristate "Generic Hotkey"
+	depends on ACPI_INTERPRETER
+	depends on EXPERIMENTAL
+	depends on !IA64_SGI_SN
+	default m
+	help
+	ACPI generic hotkey
+
 config ACPI_FAN
 	tristate "Fan"
 	depends on !IA64_SGI_SN