target/sh4: Fix mac.l with saturation enabled

target/sh4: Fix mac.l with saturation enabled

The saturation arithmetic logic in helper_macl is not correct.
I tested and verified this behavior on a SH7091.

Signed-off-by: Zack Buhman <zack@buhman.org>
Message-Id: <20240404162641.27528-2-zack@buhman.org>
[rth: Reformat helper_macl, add a test case.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit c97e8977dcacb3fa8362ee28bcee75ceb01fceaa)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>