skbuff: simplify sock_zerocopy_put

All 'struct ubuf_info' users should have a callback defined
as of commit 0a4a060b ("sock: fix zerocopy_success regression
with msg_zerocopy").

Remove the dead code path to consume_skb(), which makes
assumptions about how the structure was allocated.
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/skbuff.c

@@ -1245,12 +1245,8 @@ EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
 
 void sock_zerocopy_put(struct ubuf_info *uarg)
 {
-	if (uarg && refcount_dec_and_test(&uarg->refcnt)) {
-		if (uarg->callback)
+	if (uarg && refcount_dec_and_test(&uarg->refcnt))
 		uarg->callback(uarg, uarg->zerocopy);
-		else
-			consume_skb(skb_from_uarg(uarg));
-	}
 }
 EXPORT_SYMBOL_GPL(sock_zerocopy_put);