perf/dwc_pcie: Always register for PCIe bus notifier

BugLink: https://bugs.launchpad.net/bugs/2089340

[ Upstream commit b94b05478fb6a09033bf70c6edd03f8930a0fe24 ]

When the PCIe devices are discovered late, the driver can't find
the PCIe devices and returns in the init without registering with
the bus notifier. Due to that the devices which are discovered late
the driver can't register for this.

Register for bus notifier & driver even if the device is not found
as part of init.

Fixes: af9597adc2 ("drivers/perf: add DesignWare PCIe PMU driver")
Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
Reviewed-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240816-dwc_pmu_fix-v2-3-198b8ab1077c@quicinc.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Portia Stephens <portia.stephens@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/perf/dwc_pcie_pmu.c

@@ -728,7 +728,6 @@ static struct platform_driver dwc_pcie_pmu_driver = {
 static int __init dwc_pcie_pmu_init(void)
 {
 	struct pci_dev *pdev = NULL;
-	bool found = false;
 	int ret;
 
 	for_each_pci_dev(pdev) {
@@ -740,11 +739,7 @@ static int __init dwc_pcie_pmu_init(void)
 			pci_dev_put(pdev);
 			return ret;
 		}
-
-		found = true;
 	}
-	if (!found)
-		return -ENODEV;
 
 	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
 				      "perf/dwc_pcie_pmu:online",