share_pool: Fix ABBA deadlock

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I54I7W


CVE: NA

There is a ABBA deadlock in the process of sp_group_add_task and
proc_stat_show().

PROCESS A:
sp_group_add_task()        acquire sp_group_sem write lock
    ->sp_init_proc_stat()  acquire sp_spg_stat_sem  write lock
PROCESS B:
proc_stat_show()           acquire sp_spg_stat_sem read lock
    ->idr_proc_stat_cb()   acquire sp_group_sem read lock

Here we choose the simplest way that acquires sp_group_sem and
sp_stat_sem read lock subsequently in proc_stat_show(), since it just
has effect on the process of debug feature.

Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>