greybus: usb: constify hc_driver structures

The hc_driver structure is only passed as the first argument to
usb_create_hcd, which is declared as const.  Thus the hc_driver structure
itself can be const.

Done with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/usb.c

@@ -139,7 +139,7 @@ static int hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue, u16 wIndex,
 	return ret;
 }
 
-static struct hc_driver usb_gb_hc_driver = {
+static const struct hc_driver usb_gb_hc_driver = {
 	.description = "greybus-hcd",
 	.product_desc = "Greybus USB Host Controller",
 	.hcd_priv_size = sizeof(struct gb_usb_device),