target/mips: Introduce disas_mt_available()

target/mips: Introduce disas_mt_available()

Similarly to commit 17c2c320f3c ("Introduce ase_mt_available helper"),
introduce the disas_mt_available() one which takes a DisasContext
argument to determine whether Multi-Threading is available by
checking the MT bit of the CP0_Config3 register.

Remove the then unused ASE_MT definition.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20241024195447.44600-1-philmd@linaro.org>