accel/tcg: Name gen_goto_tb()'s TB slot index as @tb_slot_idx

accel/tcg: Name gen_goto_tb()'s TB slot index as @tb_slot_idx

tcg_gen_goto_tb() takes an unsigned index to the TB slot (0 or 1).
Declare the argument as unsigned and rename it as @tb_slot_idx
(which is more descriptive than @n) on all targets.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20251010031745.37528-1-philmd@linaro.org>