netdev-dpdk: Drop coverage counter for vhost IRQs.

The vhost library now provides finegrained statistics for guest
notifications:
- notifications for buffer reclaim by the guest,
- notifications for buffer availability to the guest,

Example before this patch:
$ ovs-appctl coverage/show |
  grep vhost_notification
vhost_notification         0.0/sec     0.000/sec        2.0283/sec   total: 7302

$ ovs-vsctl get interface vhost4 statistics |
  sed -e 's#[{}]##g' -e 's#, #\n#g' |
  grep guest_notifications
rx_q0_guest_notifications=66
tx_q0_guest_notifications=7236

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

lib/netdev-dpdk.c

@@ -78,7 +78,6 @@ VLOG_DEFINE_THIS_MODULE(netdev_dpdk);
 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
 
 COVERAGE_DEFINE(vhost_tx_contention);
-COVERAGE_DEFINE(vhost_notification);
 
 static char *vhost_sock_dir = NULL;   /* Location of vhost-user sockets */
 static bool vhost_iommu_enabled = false; /* Status of vHost IOMMU support */
@@ -188,7 +187,6 @@ static int new_device(int vid);
 static void destroy_device(int vid);
 static int vring_state_changed(int vid, uint16_t queue_id, int enable);
 static void destroy_connection(int vid);
-static void vhost_guest_notified(int vid);
 
 static const struct rte_vhost_device_ops virtio_net_device_ops =
 {
@@ -198,7 +196,6 @@ static const struct rte_vhost_device_ops virtio_net_device_ops =
     .features_changed = NULL,
     .new_connection = NULL,
     .destroy_connection = destroy_connection,
-    .guest_notified = vhost_guest_notified,
 };
 
 /* Custom software stats for dpdk ports */
@@ -4350,12 +4347,6 @@ destroy_connection(int vid)
     }
 }
 
-static
-void vhost_guest_notified(int vid OVS_UNUSED)
-{
-    COVERAGE_INC(vhost_notification);
-}
-
 /*
  * Retrieve the DPDK virtio device ID (vid) associated with a vhostuser
  * or vhostuserclient netdev.