Revert "tty: fix pid memleak in disassociate_ctty()"

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7LEZX



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This reverts commit e2944873.

Prepare to backport patch from mainline.

Signed-off-by: Yi Yang <yiyang13@huawei.com>