irqchip/ingenic: Add support for the JZ4725B SoC

The interrupt controller of the JZ4725B works the same way as the other
JZ SoCs from Ingenic; so we just add a new compatible string.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>