coresight: etm3x: Always set tracer's device mode on target CPU

coresight: etm3x: Always set tracer's device mode on target CPU

[ Upstream commit ab3fde32afe6a77e5cc60f868e44e6e09424752b ]

The ETMv3 driver shares the same issue as ETMv4 regarding race
conditions when accessing the device mode.

This commit applies the same fix: ensuring that the device mode is
modified only by the target CPU to eliminate race conditions across
CPUs.

Fixes: 22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
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/20251111-arm_coresight_power_management_fix-v6-3-f55553b6c8b3@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>