hw/loongarch: Add some devices support for 3A5000.

hw/loongarch: Add some devices support for 3A5000.

1.Add uart,virtio-net,vga and usb for 3A5000.
2.Add irq set and map for the pci host. Non pci device
use irq 0-16, pci device use 16-64.
3.Add some unimplented device to emulate guest unused
memory space.

Signed-off-by: Xiaojuan Yang <yangxiaojuan@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220606124333.2060567-38-yangxiaojuan@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>