sw64: perf: unwind: use perf's copy of kernel headers

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I73O93



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Fix this include path to use perf's copy of the kernel header rather
than the one from the root of the repo.

This fixes build errors when only applying the perf tools part of a
patchset rather than both sides.

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