ACPI / video: remove unused device_decode array

device_decode is now no longer used, so we may as well remove it.
Fixes gcc 6 warning:

drivers/acpi/acpi_video.c:221:19: warning: ‘device_decode’ defined
 but not used [-Wunused-const-variable]
 static const char device_decode[][30] = {
                   ^~~~~~~~~~~~~
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_video.c

@@ -218,13 +218,6 @@ struct acpi_video_device {
 	struct thermal_cooling_device *cooling_dev;
 };
 
-static const char device_decode[][30] = {
-	"motherboard VGA device",
-	"PCI VGA device",
-	"AGP VGA device",
-	"UNKNOWN",
-};
-
 static void acpi_video_device_notify(acpi_handle handle, u32 event, void *data);
 static void acpi_video_device_rebind(struct acpi_video_bus *video);
 static void acpi_video_device_bind(struct acpi_video_bus *video,