hw/mips: Add CPU IRQ3 delivery for KVM

hw/mips: Add CPU IRQ3 delivery for KVM

Currently, KVM/MIPS only deliver I/O interrupt via IP2, this patch add
IP3 delivery as well, because Loongson-3 based machine use both IRQ2
(CPU's IP2) and IRQ3 (CPU's IP3).

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Co-developed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Signed-off-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-Id: <1588501221-1205-4-git-send-email-chenhc@lemote.com>