powerpc/64s/radix: Enable huge vmalloc mappings

mainline inclusion
from mainline-5.13-rc1
commit 8abddd96
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZGKZ


CVE: NA

-------------------------------------------------

This reduces TLB misses by nearly 30x on a `git diff` workload on a
2-node POWER9 (59,800 -> 2,100) and reduces CPU cycles by 0.54%, due
to vfs hashes being allocated with 2MB pages.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210503091755.613393-1-npiggin@gmail.com


Conflicts:
	arch/powerpc/kernel/module.c
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Tong Tiangen <tongtiangen@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>