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/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 7699d97..77c36e63 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -259,7 +259,7 @@
 static DEFINE_MUTEX (disconnect_mutex);
 
 /* file operations needed when we register this driver */
-static struct file_operations tower_fops = {
+static const struct file_operations tower_fops = {
 	.owner =	THIS_MODULE,
 	.read  =	tower_read,
 	.write =	tower_write,