hwmon: add voltage sensor support for sw64

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56UNZ



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This patch adds SW64 PVT monitor driver to enable voltage sensor
support.

Signed-off-by: Wang Yingying <wangyingying@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>