kselftest/arm64: Fail the overall fp-stress test if any test fails

Currently fp-stress does not report a top level test result if it runs to
completion, it always exits with a return code 0. Use the ksft_finished()
helper to ensure that the exit code for the top level program reports a
failure if any of the individual tests has failed.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241017-arm64-fp-stress-exit-code-v1-1-f528e53a2321@kernel.org


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