Revert "ima: Introduce ima namespace"

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4O25G


CVE: NA

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This reverts commit a8352473.

Signed-off-by: Zhang Tianxing <zhangtianxing3@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Acked-by: Xiu <Jianfeng&lt;xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>