thermal: armada: dissociate a380 and cp110 ->init() hooks

Until now, Armada 380 and CP110 could share the same ->init() function
because their use was identical.

Prepare the support of multi-sensors support and overheat interrupt
feature by separating the initialization paths before they actually
diverge.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>