irqchip/sun4i: Move IC specific register offsets to struct

This patch moves IC specific register offsets to sun4i_irq_chip_data
struct in order to support different chips.

Signed-off-by: Mesih Kilinc <mesihkilinc@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>