net: fec: remove last_bdp from fec_enet_txq_xmit_frame()

The last_bdp is initialized to bdp, and both last_bdp and bdp are
not changed. That is to say that last_bdp and bdp are always equal.
So bdp can be used directly.

Signed-off-by: Wei Fang <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/freescale/fec_main.c

···
 				   struct xdp_frame *frame)
 {
 	unsigned int index, status, estatus;
-	struct bufdesc *bdp, *last_bdp;
+	struct bufdesc *bdp;
 	dma_addr_t dma_addr;
 	int entries_free;
 
···
 
 	/* Fill in a Tx ring entry */
 	bdp = txq->bd.cur;
-	last_bdp = bdp;
 	status = fec16_to_cpu(bdp->cbd_sc);
 	status &= ~BD_ENET_TX_STATS;
 
···
 		ebdp->cbd_esc = cpu_to_fec32(estatus);
 	}
 
-	index = fec_enet_get_bd_index(last_bdp, &txq->bd);
 	txq->tx_skbuff[index] = NULL;
 
 	/* Make sure the updates to rest of the descriptor are performed before
···
 	bdp->cbd_sc = cpu_to_fec16(status);
 
 	/* If this was the last BD in the ring, start at the beginning again. */
-	bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
+	bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
 
 	/* Make sure the update to bdp are performed before txq->bd.cur. */
 	dma_wmb();