PCI: cadence: Add cdns_plat_pcie_probe() missing return

PCI: cadence: Add cdns_plat_pcie_probe() missing return

When cdns_plat_pcie_probe() succeeds, return success instead of falling
into the error handling code.

Fixes: bd22885aa188 ("PCI: cadence: Refactor driver to use as a core library")
Link: https://lore.kernel.org/r/DM6PR19MB40271B93057D949310F0B0EDA0BF9@DM6PR19MB4027.namprd19.prod.outlook.com
Signed-off-by: Xuliang Zhang <xlzhanga@ambarella.com>
Signed-off-by: Li Chen <lchen@ambarella.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org