USB: Make file operations structs in drivers/usb const.

Making structs const prevents accidental bugs and with the proper debug
options they're protected against corruption.

Signed-off-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 98675fb..6096ead 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -90,8 +90,8 @@
 /* usbfs stuff */
 extern struct mutex usbfs_mutex;
 extern struct usb_driver usbfs_driver;
-extern struct file_operations usbfs_devices_fops;
-extern struct file_operations usbfs_device_file_operations;
+extern const struct file_operations usbfs_devices_fops;
+extern const struct file_operations usbfs_device_file_operations;
 extern void usbfs_conn_disc_event(void);
 
 extern int usbdev_init(void);