arm64/sme: Implement sysctl to set the default vector length

mainline inclusion
from mainline-v5.19-rc1
commit 12f1bacf
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8E73O
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=12f1bacfc5d9e55bedbfc7a25bf42ff6d19d1dab



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As for SVE provide a sysctl which allows the default SME vector length to
be configured.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-11-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>