livepatch/x86: check active func in consistency stack checking

hulk inclusion
category: bugfix
bugzilla: 5507/31358
CVE: NA
---------------------------

When doing consistency stack checking, if we try to patch a
function which has been patched already. We should check the
new function(not the origin func) that is activeness currently,
it's always the first entry in list func_node->func_stack.

Example :
	module : origin			livepatch v1		livepatch v2
	func   : old func A -[enable]=> new func A' -[enable]=> new func A''
	check  :		A			A'

when we try to patch function A to new function A'' by livepatch
v2, but the func A has already patched to function A' by livepatch
v1, so function A' which provided in livepatch v1 is active in the
stack instead of origin function A. Even if the long jump method is
used, we jump to the new function A' using a call without LR, the
origin function A will not appear in the stack. We must check the
active function A' in consistency stack checking.

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-By: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>