accel/tcg: Rename tcg_cpus_exec() -> tcg_cpu_exec()

accel/tcg: Rename tcg_cpus_exec() -> tcg_cpu_exec()

tcg_cpus_exec() operates on a single vCPU, rename it
as 'tcg_cpu_exec'.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20240124101639.30056-4-philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>