Revert "arm64: alternatives: Move length validation in alternative_{insn, endif}"

hulk inclusion
category: performance
bugzilla: https://e.gitee.com/open_euler/issues/list?issue=I4SCW7


CVE: NA

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This reverts commit c50395ff.

Temporary rollback, which will be backported later so that other patches
can be backported without conflict.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>