thermal: exynos: Provide initial setting for TMU's test MUX address at Exynos4412

The commit d0a0ce3e ("thermal: exynos: Add
missing definations and code cleanup") has removed setting of test MUX address
value at TMU configuration setting.

This field is not present on Exynos4210 and Exynos5 SoCs. However on Exynos4412
SoC it is required to set this field after reset because without it TMU shows
maximal available temperature, which causes immediate platform shutdown.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>