thermal: exynos: add ->tmu_clear_irqs method

Add ->tmu_clear_irqs method to struct exynos_tmu_data and use
it instead exynos_tmu_clear_irqs().  Then add ->tmu_clear_irqs
implementations for Exynos4210+ and Exynos5440.  Finally
remove no longer needed reg->tmu_int[stat,clear] abstractions
and struct exynos_tmu_registers instances.

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>