livepatch/core: Fix livepatch/state leak on error path

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WF0G


CVE: NA

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File '/proc/livepatch/state' should be removed before removing
'/proc/livepatch', otherwise following log will appear:
  remove_proc_entry: removing non-empty directory '/proc/livepatch',
  leaking at least 'state'

Fixes: c33e4283 ("livepatch/core: Allow implementation without ftrace")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>