show "rx_missed_errors" counter in interface statisics

Hi all:

    Currently OVS maintains several Statistics counters per interface. "rx_missed_errors" counter is amount them and collects pkts not received due to local resource constaints. Many ovs netdevs support collecting this counter, such as netdev-linux, netdev-dpdk, netdev-bsd and so on. But as far as I know, this counter can't be read by command "ovs-vsctl list interface <int-name>|grep statistics". I have found the root cause(may be I was wrong) is in task "iface_refresh_stats", the "rx_missed_errors" is not in the macro IFACE_STATS. So even if this counter is updated by netdev, it woundn't be read by users.

    This simple patch tries to solve this problem, many thanks for your kindly reminder.

Signed-off-by: Liu Chang <liuchang@cmss.chinamobile.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

vswitchd/bridge.c

@@ -2422,6 +2422,7 @@ iface_refresh_stats(struct iface *iface)
     IFACE_STAT(rx_frame_errors,         "rx_frame_err")             \
     IFACE_STAT(rx_over_errors,          "rx_over_err")              \
     IFACE_STAT(rx_crc_errors,           "rx_crc_err")               \
+    IFACE_STAT(rx_missed_errors,        "rx_missed_errors")         \
     IFACE_STAT(collisions,              "collisions")               \
     IFACE_STAT(rx_1_to_64_packets,      "rx_1_to_64_packets")       \
     IFACE_STAT(rx_65_to_127_packets,    "rx_65_to_127_packets")     \