tcg: Convert TARGET_SUPPORTS_MTTCG to TCGCPUOps::mttcg_supported field

tcg: Convert TARGET_SUPPORTS_MTTCG to TCGCPUOps::mttcg_supported field

Instead of having a compile-time TARGET_SUPPORTS_MTTCG definition,
have each target set the 'mttcg_supported' field in the TCGCPUOps
structure.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250405161320.76854-17-philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>