xilinx_ethlite: fix eth_can_rx() for ping-pong

The eth_can_rx() function only checks the first buffers status ("ping"). The
controller should be able to receive into "pong" when ping-pong is enabled.
Checks the active buffer (either "ping" or "pong") when determining can_rx()
rather than just testing "ping".
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@gmail.com>

hw/xilinx_ethlite.c

@@ -163,9 +163,9 @@ static const MemoryRegionOps eth_ops = {
 static int eth_can_rx(NetClientState *nc)
 {
     struct xlx_ethlite *s = DO_UPCAST(NICState, nc, nc)->opaque;
-    int r;
-    r = !(s->regs[R_RX_CTRL0] & CTRL_S);
-    return r;
+    unsigned int rxbase = s->rxbuf * (0x800 / 4);
+
+    return !(s->regs[rxbase + R_RX_CTRL0] & CTRL_S);
 }
 
 static ssize_t eth_rx(NetClientState *nc, const uint8_t *buf, size_t size)