USB: fix signedness issue in drivers/usb/gadget/ether.c

another gcc 4.1 signdness warning:

drivers/usb/gadget/ether.c:2028: warning: comparison of unsigned expression < 0 is always false

length is assigned the value of usb_ep_queue() which returns an int.
Directly after this it is checked for < 0, which can never be true.  Making
length an int makes the error check work again.
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Acked-by: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/ether.c

@@ -2014,7 +2014,7 @@ rndis_control_ack_complete (struct usb_ep *ep, struct usb_request *req)
 static int rndis_control_ack (struct net_device *net)
 {
 	struct eth_dev          *dev = netdev_priv(net);
-	u32                     length;
+	int                     length;
 	struct usb_request      *resp = dev->stat_req;
 
 	/* in case RNDIS calls this after disconnect */