thermal: exynos: remove needless tmu_status abstraction

reg->tmu_status is used only in exynos_tmu_initialize() and it
is accessed only if TMU_SUPPORT_READY_STATUS flag is set.  This
flag is not set for Exynos5440 and TMU_STATUS register offset
is identical for all other SoC types so the abstraction is not
needed and can be removed.

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>