target/arm: Expose arm_cpu_mp_affinity() in 'multiprocessing.h' header

target/arm: Expose arm_cpu_mp_affinity() in 'multiprocessing.h' header

Declare arm_cpu_mp_affinity() prototype in the new
 "target/arm/multiprocessing.h" header so units in
hw/arm/ can use it without having to include the huge
target-specific "cpu.h".

File list to include the new header generated using:

  $ git grep -lw arm_cpu_mp_affinity

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240118200643.29037-11-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>