thermal: exynos: Use IS_ERR() because regulator cannot be NULL

The NULL check in probe's error path is not needed because in that time
the regulator cannot be NULL (regulator_get() returns valid pointer or
ERR_PTR).

Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Acked-by: Lukasz Majewski <l.majewski@samsung.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/samsung/exynos_tmu.c

@@ -1396,7 +1396,7 @@ err_clk_sec:
 	if (!IS_ERR(data->clk_sec))
 		clk_unprepare(data->clk_sec);
 err_sensor:
-	if (!IS_ERR_OR_NULL(data->regulator))
+	if (!IS_ERR(data->regulator))
 		regulator_disable(data->regulator);
 
 	return ret;