ipe: fix use-after-free when auditing a newly loaded policy

new_policy() audits the policy after ipe_new_policyfs_node() publishes it
and drops the new directory's inode lock. A concurrent delete can free
the policy while ipe_audit_policy_load() is still using it.

Audit the successful load under that lock.

Fixes: f44554b5067b ("audit,ipe: add IPE auditing support")
Cc: stable@vger.kernel.org
Assisted-by: LLM
[FW: remove model name according to latest guideline]
Signed-off-by: Fan Wu <wufan@kernel.org>