selftests: arm64: Add wrapper scripts for stress tests

Add wrapper scripts which invoke fpsimd-test and sve-test with several
copies per CPU such that the context switch code will be appropriately
exercised.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200819114837.51466-6-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>