net_dma: remove duplicate assignment in dma_skb_copy_datagram_iovec

No need to compute copy twice in the frags loop in
dma_skb_copy_datagram_iovec().

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/user_dma.c

@@ -75,7 +75,7 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
 
 		end = start + skb_shinfo(skb)->frags[i].size;
 		copy = end - offset;
-		if ((copy = end - offset) > 0) {
+		if (copy > 0) {
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 			struct page *page = frag->page;