usb: hcd: constify attribute_group structures.

attribute_group are not supposed to change at runtime. All functions
working with attribute_group provided by <linux/sysfs.h> work with
const attribute_group. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -972,7 +972,7 @@ static struct attribute *usb_bus_attrs[] = {
 		NULL,
 };
 
-static struct attribute_group usb_bus_attr_group = {
+static const struct attribute_group usb_bus_attr_group = {
 	.name = NULL,	/* we want them in the same directory */
 	.attrs = usb_bus_attrs,
 };