r600g: don't flush caches if we already did so, even for a subset of the flags

Merging the flushes that are left doesn't seem to give a significant
performance improvement

Signed-off-by: Dave Airlie <airlied@redhat.com>

src/gallium/winsys/r600/drm/r600_hw_context.c

@@ -800,8 +800,8 @@ void r600_context_bo_flush(struct r600_context *ctx, unsigned flush_flags,
 	struct radeon_bo *bo;
 
 	bo = r600_bo_get_bo(rbo);
-	/* if bo has already been flush */
-	if (!(bo->last_flush ^ flush_flags)) {
+	/* if bo has already been flushed */
+	if (!(~bo->last_flush & flush_flags)) {
 		bo->last_flush &= flush_mask;
 		return;
 	}