HID: Ignore battery for Elan touchscreen on ASUS UX550

Battery status is being reported for the Elan touchscreen on ASUS
UX550 laptops despite not having a batter. It always shows either 0 or
1%.

Signed-off-by: Seth Miller <miller.seth@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 4c5f236..5ba0aa1 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -389,6 +389,7 @@
 #define USB_DEVICE_ID_TOSHIBA_CLICK_L9W	0x0401
 #define USB_DEVICE_ID_HP_X2		0x074d
 #define USB_DEVICE_ID_HP_X2_10_COVER	0x0755
+#define USB_DEVICE_ID_ASUS_UX550_TOUCHSCREEN	0x2706
 
 #define USB_VENDOR_ID_ELECOM		0x056e
 #define USB_DEVICE_ID_ELECOM_BM084	0x0061