coresight: Add PM callbacks for sink device

coresight: Add PM callbacks for sink device

Unlike system level sinks, per-CPU sinks may lose power during CPU idle
states.  Currently, this applies specifically to TRBE.  This commit
invokes save and restore callbacks for the sink in the CPU PM notifier.

If the sink provides PM callbacks but the source does not, this is
unsafe because the sink cannot be disabled safely unless the source
can also be controlled, so veto low power entry to avoid lockups.

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-v14-24-f88c4a3ecfe9@arm.com