tests/tcg/multiarch: Re-enable signals test for most guests

tests/tcg/multiarch: Re-enable signals test for most guests

With signal trampolines safely off the stack for all
guests besides hppa, we can re-enable this test.

It does show up a problem with sh4 (unrelated?),
so leave that test disabled for now.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210929130553.121567-27-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>