powerpc/64s/radix: refactor TLB flush type selection

mainline inclusion
from mainline-v5.12-rc1
commit 26418b36
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZFUI


CVE: NA

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The logic to decide what kind of TLB flush is required (local, global,
or IPI) is spread multiple times over the several kinds of TLB flushes.

Move it all into a single function which may issue IPIs if necessary,
and also returns a flush type that is to be used.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201217134731.488135-3-npiggin@gmail.com


Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Chen Wandun <chenwandun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>