OPP: rate-limit debug messages when no change in OPP is required

Otherwise, when enabling a debug build and dynamic debug in the kernel, it
quickly floods the kernel ring buffer and makes debugging of other
subsystems almost impossible, unless manually disabled.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/core.c

@@ -1091,7 +1091,7 @@ static int _set_opp(struct device *dev, struct opp_table *opp_table,
 
 	/* Return early if nothing to do */
 	if (!forced && old_opp == opp && opp_table->enabled) {
-		dev_dbg(dev, "%s: OPPs are same, nothing to do\n", __func__);
+		dev_dbg_ratelimited(dev, "%s: OPPs are same, nothing to do\n", __func__);
 		return 0;
 	}