thermal: rcar: multi channel support

R-Car thermal sensor will be multi channel sensor in next generation.
But "IRQ controlling method" and "register mapping" are
different between old/new chip.

This patch adds multi sensor support.
Then, this driver assumes there is common register
if platform has IRQ resource.

The IRQ will be supported soon.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>