coresight: etm3x: Set active path on target CPU

coresight: etm3x: Set active path on target CPU

Set the path pointer on the target CPU during ETM enable and disable.

This ensures the device mode and path pointer are updated together and
observed atomically by the CPU PM notifier.

Tested-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260515-arm_coresight_path_power_management_improvement-v14-21-f88c4a3ecfe9@arm.com