livepatch/arm64: fix unwind_frame for task

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

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commit 20380bb3 ("arm64: ftrace: fix a stack tracer's output
under function graph tracer") fix the return_to_handler showing
up in some situation.

we can directly use walk_stackframe for klp_check_calltrace instead
of klp_walk_stackframe. it's necessary because the livepatch module
need not to know the features and implementation details of ftrace.
Otherwise, this patch fix an crash when function graph enabled.

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-by: Li Bin <huawei.libin@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>