sw64: fix compile errors when CONFIG_STACKTRACE is not set

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56QAM



--------------------------------

The stacktrace.c should be always compiled.

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