hw/net/rtl8139: Simplify if/else statement

Rewrite:

      if (E) {
          return A;
      } else {
          return B;
      }
      /* EOF */
  }

as:

      if (E) {
          return A;
      }
      return B;
  }

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/rtl8139.c

@@ -808,11 +808,11 @@ static int rtl8139_can_receive(NetClientState *nc)
         /* ??? Flow control not implemented in c+ mode.
            This is a hack to work around slirp deficiencies anyway.  */
         return 1;
-    } else {
-        avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr,
-                     s->RxBufferSize);
-        return (avail == 0 || avail >= 1514 || (s->IntrMask & RxOverflow));
     }
+
+    avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr,
+                 s->RxBufferSize);
+    return avail == 0 || avail >= 1514 || (s->IntrMask & RxOverflow);
 }
 
 static ssize_t rtl8139_do_receive(NetClientState *nc, const uint8_t *buf, size_t size_, int do_interrupt)