kselftest/arm64: Limit the maximum VL we try to set via ptrace

When SVE was initially merged we chose to export the maximum VQ in the ABI
as being 512, rather more than the architecturally supported maximum of 16.
For the ptrace tests this results in us generating a lot of test cases and
hence log output which are redundant since a system couldn't possibly
support them. Instead only check values up to the current architectural
limit, plus one more so that we're covering the constraining of higher
vector lengths.

This makes no practical difference to our test coverage, speeds things up
on slower consoles and makes the output much more managable.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230111-arm64-kselftest-ptrace-max-vl-v1-1-8167f41d1ad8@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>