irqchip/irq-ingenic-tcu: Fix COMPILE_TEST building
While do COMPILE_TEST building, if GENERIC_IRQ_CHIP is
not selected, it fails:
drivers/irqchip/irq-ingenic-tcu.o: In function `ingenic_tcu_intc_cascade':
irq-ingenic-tcu.c:(.text+0x13f): undefined reference to `irq_get_domain_generic_chip'
drivers/irqchip/irq-ingenic-tcu.o: In function `ingenic_tcu_irq_init':
irq-ingenic-tcu.c:(.init.text+0x97): undefined reference to `irq_generic_chip_ops'
irq-ingenic-tcu.c:(.init.text+0xdd): undefined reference to `__irq_alloc_domain_generic_chips'
irq-ingenic-tcu.c:(.init.text+0x10b): undefined reference to `irq_get_domain_generic_chip'