target/mips: Fix MSA BZ/BNZ opcodes displacement

target/mips: Fix MSA BZ/BNZ opcodes displacement

The PC offset is *signed*.

Cc: qemu-stable@nongnu.org
Reported-by: Sergey Evlashev <vectorchiefrocks@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1624
Fixes: c7a9ef7517 ("target/mips: Introduce decode tree bindings for MSA ASE")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230914085807.12241-1-philmd@linaro.org>
(cherry picked from commit 04591b3ddd9a96b9298a1dd437a6464ab55e62ee)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>