sw64: add a misc device to chip_vt.dts for memory-hotplug

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56WV8



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This is an emulated device used to communicate with the memory-hotplug
device on the qemu side, so the device is added to device tree for
guest os.

Signed-off-by: Lu Feifei <lufeifei@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>