Input: synaptics_usb - constify usb_device_id

usb_device_id are not supposed to change at runtime. All functions
working with usb_device_id provided by <linux/usb.h> work with
const usb_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/synaptics_usb.c

@@ -525,7 +525,7 @@ static int synusb_reset_resume(struct usb_interface *intf)
 	return synusb_resume(intf);
 }
 
-static struct usb_device_id synusb_idtable[] = {
+static const struct usb_device_id synusb_idtable[] = {
 	{ USB_DEVICE_SYNAPTICS(TP, SYNUSB_TOUCHPAD) },
 	{ USB_DEVICE_SYNAPTICS(INT_TP, SYNUSB_TOUCHPAD) },
 	{ USB_DEVICE_SYNAPTICS(CPAD,