sw64: fix "unwind: target platform=sw_64 is not supported"

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6IL86



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Change the target names and file names to match the compile option
"-lunwind-sw_64".

Signed-off-by: He Chuyue <hechuyue@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>