percpu: factor out pcpu_check_block_hint()

mainline inclusion
from mainline-v5.14-rc1
commit 8ea2e1e3
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4BE79


CVE: NA

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Factor out the pcpu_check_block_hint() helper, which will be useful
in the future. The new function checks if the allocation can likely
fit within the contig hint.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
(cherry picked from commit 8ea2e1e3)
Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>