staging: greybus: hid: Constify lowlevel HID driver

Since commit 52d22534 ("HID: Make lowlevel driver structs const")
the lowlevel HID drivers are only exposed as const.

Take advantage of this to constify the underlying structure, too.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230130-hid-const-ll-driver-v1-9-3fc282b3b1d0@weissschuh.netSigned-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/staging/greybus/hid.c

@@ -381,7 +381,7 @@ static int gb_hid_power(struct hid_device *hid, int lvl)
 }
 
 /* HID structure to pass callbacks */
-static struct hid_ll_driver gb_hid_ll_driver = {
+static const struct hid_ll_driver gb_hid_ll_driver = {
 	.parse = gb_hid_parse,
 	.start = gb_hid_start,
 	.stop = gb_hid_stop,