dell-laptop: Update rfkill state on kill switch

The rfkill interface on Dells only sends a notification that the switch
has been changed via the keyboard controller. Add a filter so we can
pick these notifications up and update the rfkill state appropriately.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index f526e73..6848f21 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -79,6 +79,7 @@
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on RFKILL || RFKILL = n
 	depends on POWER_SUPPLY
+	depends on SERIO_I8042
 	default n
 	---help---
 	This driver adds support for rfkill and backlight control to Dell