virgl: count the calls to gl_block

In virgl_cmd_resource_flush(), when several consoles are updated, it
needs to keep blocking until all spice gl draws are done. This fixes an
assert() in spice when using multiple monitors with virgl.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 1465911849-30423-2-git-send-email-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/hw/virtio/virtio-gpu.h

@@ -107,7 +107,7 @@ typedef struct VirtIOGPU {
 
     bool use_virgl_renderer;
     bool renderer_inited;
-    bool renderer_blocked;
+    int renderer_blocked;
     QEMUTimer *fence_poll;
     QEMUTimer *print_stats;