contrib/vhost-user-blk: Clean up deallocation of VuVirtqElement

We allocate VuVirtqElement with g_malloc() in
virtqueue_alloc_element(), but free it with free() in
vhost-user-blk.c.  Harmless, but use g_free() anyway.

One of the calls is guarded by a "not null" condition.  Useless,
because it cannot be null (it's dereferenced right before), and even
it it could be, free() and g_free() do the right thing.  Drop the
conditional.

Fixes: Coverity CID 1490290
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220630085219.1305519-1-armbru@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

contrib/vhost-user-blk/vhost-user-blk.c

@@ -106,10 +106,7 @@ static void vub_req_complete(VubReq *req)
                   req->size + 1);
     vu_queue_notify(vu_dev, req->vq);
 
-    if (req->elem) {
-        free(req->elem);
-    }
-
+    g_free(req->elem);
     g_free(req);
 }
 
@@ -243,7 +240,7 @@ static int vub_virtio_process_req(VubDev *vdev_blk,
     /* refer to hw/block/virtio_blk.c */
     if (elem->out_num < 1 || elem->in_num < 1) {
         fprintf(stderr, "virtio-blk request missing headers\n");
-        free(elem);
+        g_free(elem);
         return -1;
     }
 
@@ -325,7 +322,7 @@ static int vub_virtio_process_req(VubDev *vdev_blk,
     return 0;
 
 err:
-    free(elem);
+    g_free(elem);
     g_free(req);
     return -1;
 }