hw/net: Make NetCanReceive() return a boolean

The NetCanReceive handler return whether the device can or
can not receive new packets. Make it obvious by returning
a boolean type.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index be9a0af..70aca7e 100644
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -793,23 +793,23 @@
     return !(s->RxRingAddrLO == 0 && s->RxRingAddrHI == 0);
 }
 
-static int rtl8139_can_receive(NetClientState *nc)
+static bool rtl8139_can_receive(NetClientState *nc)
 {
     RTL8139State *s = qemu_get_nic_opaque(nc);
     int avail;
 
     /* Receive (drop) packets if card is disabled.  */
     if (!s->clock_enabled) {
-        return 1;
+        return true;
     }
     if (!rtl8139_receiver_enabled(s)) {
-        return 1;
+        return true;
     }
 
     if (rtl8139_cp_receiver_enabled(s) && rtl8139_cp_rx_valid(s)) {
         /* ??? Flow control not implemented in c+ mode.
            This is a hack to work around slirp deficiencies anyway.  */
-        return 1;
+        return true;
     }
 
     avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr,