perf/arm_cspmu: Assign parents for event_source devices

Currently all these devices appear directly under /sys/devices/
Only root busses should appear there, so instead assign the pmu->dev
parents to be the platform device.

Link: https://lore.kernel.org/linux-cxl/ZCLI9A40PJsyqAmq@kroah.com/
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240412161057.14099-8-Jonathan.Cameron@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: jic23

drivers/perf/arm_cspmu/arm_cspmu.c

@@ -1206,6 +1206,7 @@ static int arm_cspmu_register_pmu(struct arm_cspmu *cspmu)
 	cspmu->pmu = (struct pmu){
 		.task_ctx_nr	= perf_invalid_context,
 		.module		= cspmu->impl.module,
+		.parent		= cspmu->dev,
 		.pmu_enable	= arm_cspmu_enable,
 		.pmu_disable	= arm_cspmu_disable,
 		.event_init	= arm_cspmu_event_init,