net: ethernet: nb8800: remove redundant pointer rxd

Pointer rxd is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'rxb' set but not used [-Wunused-but-set-variable]
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aurora/nb8800.c

@@ -304,12 +304,10 @@ static int nb8800_poll(struct napi_struct *napi, int budget)
 
 again:
 	do {
-		struct nb8800_rx_buf *rxb;
 		unsigned int len;
 
 		next = (last + 1) % RX_DESC_COUNT;
 
-		rxb = &priv->rx_bufs[next];
 		rxd = &priv->rx_descs[next];
 
 		if (!rxd->report)