ima: fix a memory leak in ima_del_digest_data_entry

hulk inclusion
category: bugfix
bugzilla: 46797
CVE: NA
Reference: https://gitee.com/openeuler/kernel/issues/I3C03N



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This patch fix a memory leak problem when deleting digest list.

hlist_del_rcu in ima_del_digest_data_entry only deletes the digest
struct from the linked list without releasing the memory it uses.

Signed-off-by: Zhang Tianxing <zhangtianxing3@huawei.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>