perf/imx_ddr: Assign parents for event_source devices

Currently all this device appear 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/
Cc: Frank Li <Frank.li@nxp.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240412161057.14099-16-Jonathan.Cameron@huawei.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/perf/fsl_imx8_ddr_perf.c

@@ -651,6 +651,7 @@ static int ddr_perf_init(struct ddr_pmu *pmu, void __iomem *base,
 	*pmu = (struct ddr_pmu) {
 		.pmu = (struct pmu) {
 			.module	      = THIS_MODULE,
+			.parent      = dev,
 			.capabilities = PERF_PMU_CAP_NO_EXCLUDE,
 			.task_ctx_nr = perf_invalid_context,
 			.attr_groups = attr_groups,