livepatch/core: Fix possible issue that old function is not checked

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7ZH67


CVE: NA

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After patch being enabled, the first few instructions would be
modified to jump to the new function, then callers of old function
would jump to new function but always through the old function.

Therefore when enabling a new patch or disable a patch on the old
function, we should always consider that old function is running.
Otherwise, there may be situations where old functions are being
modified before jumping to new function and cause issues.

Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>