x86: Fix __get_wchan() for !STACKTRACE

mainline inclusion
from mainline-v5.16-rc1
commit 5d1ceb3969b6b2e47e2df6d17790a7c5a20fcbb4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5BKYL


CVE: NA

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

Use asm/unwind.h to implement wchan, since we cannot always rely on
STACKTRACE=y.

Fixes: bc9bbb81730e ("x86: Fix get_wchan() to support the ORC unwinder")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20211022152104.137058575@infradead.org


Signed-off-by: Lin Yujun <linyujun809@huawei.com>
Reviewed-by: Zhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>