mm/sharepool: Fix a double free problem caused by init_local_group

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I64Y5Y



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If local_group_add_task fails in init_local_group. ida free the
same id twice.

init_local_group
  local_group_add_task    // failed
  goto free_spg

free_spg:
  free_sp_group_locked
    free_sp_group_id      // free spg->id
free_spg_id:
  free_new_spg_id         // double free spg->id

To fix it, return before calling free_new_spg_id.

Signed-off-by: Chen Jun <chenjun102@huawei.com>