h264: Don't set num_slices anymore

The num_slices parameter was improperly set to the number of reference
frames, which is incorrect.

Add a counter for the number of slices per surface, and set num_slices to
that value.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

src/surface.c

@@ -161,6 +161,7 @@ VAStatus SunxiCedrusCreateSurfaces(VADriverContextP context, int width,
 
 		memset(&surface_object->params, 0,
 		       sizeof(surface_object->params));
+		surface_object->slices_count = 0;
 		surface_object->slices_size = 0;
 
 		surface_object->request_fd = -1;