tests/tcg/arm: Remove test-arm-iwmmxt test

tests/tcg/arm: Remove test-arm-iwmmxt test

The test-arm-iwmmmxt test isn't testing what it thinks it's testing.

If you run it with a CPU type that supports iwMMXt then it will crash
immediately with a SIGILL, because (even with -marm) GCC will link it
against startup code that is in Thumb mode, and no iwMMXt CPU has
Thumb:

00010338 <_start>:
   10338:       f04f 0b00       mov.w   fp, #0
   1033c:       f04f 0e00       mov.w   lr, #0

If you run it with a CPU type which does *not* support iwMMXt, which
is what 'make check-tcg' does, then QEMU will not try to handle the
insns as iwMMXt.  Instead the translator turns them into illegal
instructions.  Then in the linux-user cpu_loop() code we identify
them as FPA11 instructions inside emulate_arm_fpa11(), because the
FPA11 happened to use the same coprocessor number as these iwMMXt
insns.  So we execute a completely different set of FPA11 insns,
which means we don't crash, but we will print garbage to stdout.
Then the test binary always exits with a 0 return code, so 'make
check-tcg' thinks the test passes.

Modern gnueabihf toolchains assume in their startup code that the CPU
is not so old as to not support Thumb, so there's no way to get them
to generate a binary that actually does what the test wants.  Since
we're deprecating iwMMXt emulation anyway, it's not worth trying to
salvage the test case to get it to really test the iwMMXt insns.

Delete the test entirely.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250127112715.2936555-3-peter.maydell@linaro.org