rtc: brcmstb-waketimer: add missed clk_disable_unprepare

This driver forgets to disable and unprepare clock when remove.
Add a call to clk_disable_unprepare to fix it.

Fixes: c4f07ece ("rtc: brcmstb-waketimer: Add Broadcom STB wake-timer")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20191105160043.20018-1-hslester96@gmail.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-brcmstb-waketimer.c

@@ -275,6 +275,7 @@ static int brcmstb_waketmr_remove(struct platform_device *pdev)
 	struct brcmstb_waketmr *timer = dev_get_drvdata(&pdev->dev);
 
 	unregister_reboot_notifier(&timer->reboot_notifier);
+	clk_disable_unprepare(timer->clk);
 
 	return 0;
 }