HID: make USB device id constant

The id_table field of the struct usb_device_id is constant in <linux/usb.h>
so it is worth to make the initialization data also constant.

The semantic match that finds this kind of pattern is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
disable decl_init,const_decl_init;
identifier I1, I2, x;
@@
	struct I1 {
	  ...
	  const struct I2 *x;
	  ...
	};
@s@
identifier r.I1, y;
identifier r.x, E;
@@
	struct I1 y = {
	  .x = E,
	};
@c@
identifier r.I2;
identifier s.E;
@@
	const struct I2 E[] = ... ;
@depends on !c@
identifier r.I2;
identifier s.E;
@@
+	const
	struct I2 E[] = ...;
// </smpl>
Signed-off-by: Márton Németh <nm127@freemail.hu>
Cc: Julia Lawall <julia@diku.dk>
Cc: cocci@diku.dk
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/usbhid/hid-core.c

@@ -1342,7 +1342,7 @@ static int hid_reset_resume(struct usb_interface *intf)
 
 #endif /* CONFIG_PM */
 
-static struct usb_device_id hid_usb_ids [] = {
+static const struct usb_device_id hid_usb_ids[] = {
 	{ .match_flags = USB_DEVICE_ID_MATCH_INT_CLASS,
 		.bInterfaceClass = USB_INTERFACE_CLASS_HID },
 	{ }						/* Terminating entry */