VMXNET3: initialize rx_ridx to eliminate compile warning

  Gcc report "hw/vmxnet3.c:972: error: ‘rx_ridx’ may be used
uninitialized in this function", so fix it.
Signed-off-by: NWenchao Xia <xiawenc@linux.vnet.ibm.com>
Message-id: 1364264646-27542-1-git-send-email-xiawenc@linux.vnet.ibm.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/vmxnet3.c

@@ -969,7 +969,7 @@ vmxnet3_indicate_packet(VMXNET3State *s)
     struct Vmxnet3_RxDesc rxd;
     bool is_head = true;
     uint32_t rxd_idx;
-    uint32_t rx_ridx;
+    uint32_t rx_ridx = 0;
 
     struct Vmxnet3_RxCompDesc rxcd;
     uint32_t new_rxcd_gen = VMXNET3_INIT_GEN;