svga: include sample count in surface_size() computation

Use MAX2() because sampleCount will be zero for non-MSAA surfaces.
No Piglit regressions.

Reviewed-by: Charmaine Lee <charmainel@vmware.com>

src/gallium/drivers/svga/svga_screen_cache.c

@@ -69,7 +69,7 @@ surface_size(const struct svga_host_surface_cache_key *key)
       total_size += img_size;
    }
 
-   total_size *= key->numFaces * key->arraySize;
+   total_size *= key->numFaces * key->arraySize * MAX2(1, key->sampleCount);
 
    return total_size;
 }