thermal: exynos: fix setting rising_threshold for Exynos5433

Add missing clearing of the previous value when setting rising
temperature threshold.
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/samsung/exynos_tmu.c

@@ -577,6 +577,7 @@ static int exynos5433_tmu_initialize(struct platform_device *pdev)
 		threshold_code = temp_to_code(data, temp);
 
 		rising_threshold = readl(data->base + rising_reg_offset);
+		rising_threshold &= ~(0xff << j * 8);
 		rising_threshold |= (threshold_code << j * 8);
 		writel(rising_threshold, data->base + rising_reg_offset);