hw/intc: Add Loongson LIOINTC support

hw/intc: Add Loongson LIOINTC support

Loongson-3 has an integrated liointc (Local I/O Interrupt Controller).
It is similar to Goldfish interrupt controller, but more powerful (e.g.,
it can route external interrupt to multi-cores).

Documents about Loongson-3's liointc:
1, https://wiki.godson.ac.cn/ip_block:liointc;
2, The "I/O中断" section of Loongson-3's user mannual, part 1.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-Id: <1592995531-32600-3-git-send-email-chenhc@lemote.com>