hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7R8WG

--------------------------------

A previous commit made del_timer[_sync]() obsolete and unexported, which
caused kabi to break. So making del_timer[_sync]() exported, the same as
before.
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
(cherry picked from commit ec2d781a)