kselftest/arm64: sme: Add SME support to vlset

kselftest/arm64: sme: Add SME support to vlset

The Scalable Matrix Extenions (SME) introduces additional register state
with configurable vector lengths, similar to SVE but configured separately.
Extend vlset to support configuring this state with a --sme or -s command
line option.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-30-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>