thermal: exynos: Directly return 0 instead of using local ret variable

The 'ret' variable in exynos5440_tmu_initialize() is initialized to 0
and returned as is. Replace it with direct return statement. This also
fixes coccinelle warning:
drivers/thermal/samsung/exynos_tmu.c:611:5-8: Unneeded variable: "ret". Return "0" on line 654

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>