X86 drivers: Introduce msi-wmi driver

This driver serves backlight (including switching) and volume up/down
keys for MSI machines providing a specific wmi interface:
551A1F84-FBDD-4125-91DB-3EA8F44F1D45
B6F3EEF2-3D2F-49DC-9DE3-85BCE18C62F2

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: Carlos Corbacho <carlos@strangeworlds.co.uk>
CC: Matthew Garrett <mjg59@srcf.ucam.org>
Tested-by: Matt Chen <machen@novell.com>
Reviewed-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 55ca39d..98ec6bd 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -365,6 +365,16 @@
 	  It is safe to enable this driver even if your DSDT doesn't define
 	  any ACPI-WMI devices.
 
+config MSI_WMI
+	tristate "MSI WMI extras"
+	depends on ACPI_WMI
+	depends on INPUT
+	help
+	 Say Y here if you want to support WMI-based hotkeys on MSI laptops.
+
+	 To compile this driver as a module, choose M here: the module will
+	 be called msi-wmi.
+
 config ACPI_ASUS
 	tristate "ASUS/Medion Laptop Extras (DEPRECATED)"
 	depends on ACPI