sched/topology: Fix exceptional memory access in sd_llc_free_all()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6YJJQ


CVE: NA

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

The function sd_llc_free_all() will be called to release allocated
resources when space allocation for the scheduling domain
structure fails. However, this function did not check if sd
is a null pointer when releasing sdd resources, resulting in
an error: "Unable to handle kernel paging request at virtual
address".

Fix this issue by adding null pointer discrimination.

Fixes: 79bec4c6 ("sched/topology: Provide hooks to allocate data shared per LLC")
Signed-off-by: Xia Fukun <xiafukun@huawei.com>
Reviewed-by: songping yu <yusongping@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>