thermal: exynos: replace threshold_falling check by Exynos SoC type one

Replace pdata->threshold_falling check for non-zero value in
exynos_tmu_initialize() by an explicit check for a SoC type
(all SoC types except Exynos5440 have pdata->threshold_falling
assigned to non-zero value in their struct exynos_tmu_registers
instances).

This is a preparation for introducing per-SoC type tmu_initialize
method.

There should be no functional changes caused by this patch.

Cc: Amit Daniel Kachhap <amit.daniel@samsung.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/samsung/exynos_tmu.c

@@ -231,7 +231,7 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
 						pdata->trigger_levels[i]);
 			rising_threshold &= ~(0xff << 8 * i);
 			rising_threshold |= threshold_code << 8 * i;
-			if (pdata->threshold_falling) {
+			if (data->soc != SOC_ARCH_EXYNOS5440) {
 				threshold_code = temp_to_code(data,
 						pdata->trigger_levels[i] -
 						pdata->threshold_falling);