cpufreq: mediatek: Convert pr_warn() to pr_debug()

With multi-platform build images, this shows a message on non mediatek
platforms, which is unnecessary. Convert pr_warn() to pr_debug() here.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Acked-by: NSean Wang <sean.wang@mediatek.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/mediatek-cpufreq.c

@@ -578,7 +578,7 @@ static int __init mtk_cpufreq_driver_init(void)
 	match = of_match_node(mtk_cpufreq_machines, np);
 	of_node_put(np);
 	if (!match) {
-		pr_warn("Machine is not compatible with mtk-cpufreq\n");
+		pr_debug("Machine is not compatible with mtk-cpufreq\n");
 		return -ENODEV;
 	}