This patch fixes below warning spotted by kbuild test robot when building
with ARCH=powerpc:
   drivers/clocksource/timer-stm32.c: In function 'stm32_clockevent_init':
>> drivers/clocksource/timer-stm32.c:140:9: warning: large integer implicitly
	truncated to unsigned type [-Woverflow]
     writel_relaxed(~0UL, data->base + TIM_ARR);
The fix consists in using 0U instead of 0UL.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
        }
 
        /* Detect whether the timer is 16 or 32 bits */
-       writel_relaxed(~0UL, data->base + TIM_ARR);
+       writel_relaxed(~0U, data->base + TIM_ARR);
        max_delta = readl_relaxed(data->base + TIM_ARR);
-       if (max_delta == ~0UL) {
+       if (max_delta == ~0U) {
                prescaler = 1;
                bits = 32;
        } else {