vhost: move spdk_vhost_init/fini to vhost library

Althrough the two functions are empty now, but they are not
vhost_scsi specific.

Change-Id: I331a455374f7dd92fd76cab255a43072baceb0dd
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-on: https://review.gerrithub.io/389477
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>

lib/vhost/vhost.c

@@ -1166,4 +1166,15 @@ spdk_vhost_unlock(void)
 	pthread_mutex_unlock(&g_spdk_vhost_mutex);
 }
 
+int
+spdk_vhost_init(void)
+{
+	return 0;
+}
+
+void
+spdk_vhost_fini(void)
+{
+}
+
 SPDK_LOG_REGISTER_TRACE_FLAG("vhost_ring", SPDK_TRACE_VHOST_RING)

lib/vhost/vhost_scsi.c

@@ -1127,17 +1127,6 @@ err:
 	return -1;
 }
 
-int
-spdk_vhost_init(void)
-{
-	return 0;
-}
-
-void
-spdk_vhost_fini(void)
-{
-}
-
 static void
 spdk_vhost_scsi_config_json(struct spdk_vhost_dev *vdev, struct spdk_json_write_ctx *w)
 {