perf/arm_pmu: Assign parents for event_source devices

perf/arm_pmu: Assign parents for event_source devices

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

Link: https://lore.kernel.org/linux-cxl/ZCLI9A40PJsyqAmq@kroah.com/
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20240412161057.14099-17-Jonathan.Cameron@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>