acpi_video: kernel build error if !INPUT

Commit e9dab196
(ACPI video hotkey: export missing ACPI video hotkey events via input layer)
exports ACPI video hotkey events via input layer. But this breaks kernel
build if ACPI_VIDEO && !INPUT:

 LD      .tmp_vmlinux1
drivers/built-in.o: In function `acpi_video_bus_remove':
drivers/acpi/video.c:2007: undefined reference to `input_unregister_device'
    ...
Signed-off-by: NAndreas Herrmann <aherrman@arcor.de>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/Kconfig

@@ -117,6 +117,7 @@ config ACPI_BUTTON
 config ACPI_VIDEO
 	tristate "Video"
 	depends on X86 && BACKLIGHT_CLASS_DEVICE && VIDEO_OUTPUT_CONTROL
+	depends on INPUT
 	help
 	  This driver implement the ACPI Extensions For Display Adapters
 	  for integrated graphics devices on motherboard, as specified in