USB: "sparse" cleanups for usb gadgets

This removes complaints about the gadget stack which are generated by
the currrent "sparse":  it doesn't like the fact that zero is the null
pointer.  (Last I checked, C guarantees that's correct ...)

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

diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c
index a337673..593e235 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -1723,7 +1723,8 @@
 		size += sizeof (struct rndis_packet_msg_type);
 	size -= size % dev->out_ep->maxpacket;
 
-	if ((skb = alloc_skb (size + NET_IP_ALIGN, gfp_flags)) == 0) {
+	skb = alloc_skb(size + NET_IP_ALIGN, gfp_flags);
+	if (skb == NULL) {
 		DEBUG (dev, "no rx skb\n");
 		goto enomem;
 	}