sb1250-mac: duplicate setting of bit V_MAC_RX_PL_THRSH(4) in sbmac_channel_start()

The bit V_MAC_RX_PL_THRSH(4) was already set a few lines higher.
Signed-off-by: NRoel Kluin <roel.kluin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/sb1250-mac.c

@@ -1476,7 +1476,6 @@ static void sbmac_channel_start(struct sbmac_softc *s)
 		V_MAC_TX_RL_THRSH(4) |
 		V_MAC_RX_PL_THRSH(4) |
 		V_MAC_RX_RD_THRSH(4) |	/* Must be '4' */
-		V_MAC_RX_PL_THRSH(4) |
 		V_MAC_RX_RL_THRSH(8) |
 		0;