mm: share_pool: adjust sp_alloc behavior when coredump

ascend inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4MUV2


CVE: NA

when sp_alloc is being executed ont the whole sharepool group,
and one process coredumps, allocation will skip the coredumped process and
continue on the rest processes in the group.

Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>