ppc4xx: Change receive buffer handling in the 4xx emac driver

This change fixes a bug in the receive buffer handling, that
could lead to problems upon high network traffic (broadcasts...).

Signed-off-by: Stefan Roese <sr@denx.de>

cpu/ppc4xx/4xx_enet.c

diff --git a/cpu/ppc4xx/4xx_enet.c b/cpu/ppc4xx/4xx_enet.c
index 1200d02..b90363f 100644
--- a/cpu/ppc4xx/4xx_enet.c
+++ b/cpu/ppc4xx/4xx_enet.c
@@ -1415,10 +1415,8 @@
 			if ((MAL_RX_CTRL_EMPTY & hw_p->rx[i].ctrl)
 			    || (loop_count >= NUM_RX_BUFF))
 				break;
+
 			loop_count++;
-			hw_p->rx_slot++;
-			if (NUM_RX_BUFF == hw_p->rx_slot)
-				hw_p->rx_slot = 0;
 			handled++;
 			data_len = (unsigned long) hw_p->rx[i].data_len;	/* Get len */
 			if (data_len) {
@@ -1468,6 +1466,10 @@
 				if (NUM_RX_BUFF == hw_p->rx_i_index)
 					hw_p->rx_i_index = 0;
 
+				hw_p->rx_slot++;
+				if (NUM_RX_BUFF == hw_p->rx_slot)
+					hw_p->rx_slot = 0;
+
 				/*  AS.HARNOIS
 				 * free receive buffer only when
 				 * buffer has been handled (eth_rx)