clk: tegra: tegra124-emc: Fix clock imbalance in emc_set_timing()

After calling clk_prepare_enable(), clk_disable_unprepare() needs
be called when prepare_timing_change() failed.

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Yang Yingliang <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/clk/tegra/clk-tegra124-emc.c

···
 	div = timing->parent_rate / (timing->rate / 2) - 2;
 
 	err = tegra->prepare_timing_change(emc, timing->rate);
-	if (err)
+	if (err) {
+		clk_disable_unprepare(timing->parent);
 		return err;
+	}
 
 	spin_lock_irqsave(tegra->lock, flags);