sw64: mark sched_clock() as notrace

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I645RC



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sched_clock() of SW64 has no notrace mark like the generic declaration
and it will cause kernel crash in ftrace selftests. Add notrace to fix
it.

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