r600g: remove useless call to u_upload_flush

No regressions found with :
- piglit (quick.tests)
- Unigine Heaven
- Lightsmark
- openarena
- Imprudence (Second Life fork)

agd5f Note: this patch was previously reverted due to piglit
regressions, but I'm not able to reproduce them here.
See this bug:
https://bugs.freedesktop.org/show_bug.cgi?id=34008
and discussion:
http://lists.freedesktop.org/archives/dri-devel/2011-June/011996.html

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>

src/gallium/drivers/r600/r600_pipe.c

@@ -138,11 +138,6 @@ static void r600_flush(struct pipe_context *ctx,
 	dc++;
 #endif
 	r600_context_flush(&rctx->ctx);
-
-	/* XXX This shouldn't be really necessary, but removing it breaks some tests.
-	 * Needless buffer reallocations may significantly increase memory consumption,
-	 * so getting rid of this call is important. */
-	u_upload_flush(rctx->vbuf_mgr->uploader);
 }
 
 static void r600_update_num_contexts(struct r600_screen *rscreen, int diff)