driver model: constify attribute groups

Let attribute group vectors be declared "const".  We'd
like to let most attribute metadata live in read-only
sections... this is a start.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index e2a8cfa..c0e0ae2 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -152,8 +152,8 @@
 extern const char *usbcore_name;
 
 /* sysfs stuff */
-extern struct attribute_group *usb_device_groups[];
-extern struct attribute_group *usb_interface_groups[];
+extern const struct attribute_group *usb_device_groups[];
+extern const struct attribute_group *usb_interface_groups[];
 
 /* usbfs stuff */
 extern struct mutex usbfs_mutex;