Add Ingenic JZ4760 and X1000 and X1500 irqchip support v4.

[Zhou Yanjie]

v1->v2: Replace "__fls(pending)" with "bit" in function "generic_handle_irq".
v2->v3: Add support for probing irq-ingenic driver on JZ4760 and X1500 Soc.
v3->v4: Combined with patches 5 and 7, combined with patches 4, 6 and 8.