watchdog: davinci: Use div64_ul instead of do_div

do_div() does a 64-by-32 division. Here the divisor is an unsigned long
which on some platforms is 64 bit wide. So use div64_ul instead of do_div
to avoid a possible truncation.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211125014924.46297-1-deng.changcheng@zte.com.cn
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/davinci_wdt.c

@@ -134,7 +134,7 @@ static unsigned int davinci_wdt_get_timeleft(struct watchdog_device *wdd)
 	timer_counter = ioread32(davinci_wdt->base + TIM12);
 	timer_counter |= ((u64)ioread32(davinci_wdt->base + TIM34) << 32);
 
-	do_div(timer_counter, freq);
+	timer_counter = div64_ul(timer_counter, freq);
 
 	return wdd->timeout - timer_counter;
 }