sw64: register a suspend entry

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5XTK7



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Since the method of powering down the core is strongly coupled with the
implementation of hardware designing, this part is put into BIOS now. So
kernel need to get and register the address of the sleep entry from BIOS,
which would be used in sleep interrupt entry of HMCode.

Signed-off-by: Zhao Yihan <zhaoyihan@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>