thermal: samsung: change base_common to more meaningful base_second

On Exynos5440 and Exynos5420 there are registers common
across the TMU channels.

To support that, we introduced a ADDRESS_MULTIPLE flag in the
driver and the 2nd set of register base and size are provided
in the "reg" property of the node.

As per Amit's suggestion, this patch changes the base_common
to base_second and SHARED_MEMORY to ADDRESS_MULTIPLE.

Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Acked-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>