cxgb3: Fix T3C MAC max packet size access

Max packet size is not the only field in T3C's High Water Mark register.
Mask the register to access this field.
Signed-off-by: NDivy Le Ray <divy@chelsio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/cxgb3/xgmac.c

@@ -447,11 +447,12 @@ int t3_mac_set_speed_duplex_fc(struct cmac *mac, int speed, int duplex, int fc)
 
 	val = t3_read_reg(adap, A_XGM_RXFIFO_CFG + oft);
 	val &= ~V_RXFIFOPAUSEHWM(M_RXFIFOPAUSEHWM);
-	if (fc & PAUSE_TX)
-		val |= V_RXFIFOPAUSEHWM(rx_fifo_hwm(
-						t3_read_reg(adap,
-						A_XGM_RX_MAX_PKT_SIZE
-						+ oft)) / 8);
+	if (fc & PAUSE_TX) {
+		u32 rx_max_pkt_size =
+		    G_RXMAXPKTSIZE(t3_read_reg(adap,
+					       A_XGM_RX_MAX_PKT_SIZE + oft));
+		val |= V_RXFIFOPAUSEHWM(rx_fifo_hwm(rx_max_pkt_size) / 8);
+	}
 	t3_write_reg(adap, A_XGM_RXFIFO_CFG + oft, val);
 
 	t3_set_reg_field(adap, A_XGM_TX_CFG + oft, F_TXPAUSEEN,