kselftest/arm64: Add test coverage for NT_ARM_TLS

In preparation for extending support for NT_ARM_TLS to cover additional
TPIDRs add some tests for the existing interface. Do this in a generic
ptrace test program to provide a place to collect additional tests in
the future.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154921.837871-2-broonie@kernel.org


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