PCI: rcar: Fix error exit path

Commit 90634e85 ("PCI: rcar: Convert PCI scan API to
pci_scan_root_bus_bridge()") converted PCI root bus scan API to the new
pci_scan_root_bus_bridge() API; in the process some error paths were not
updated correctly which may cause memory leaks.

Fix the driver error exit path reinstating the previous correct
error exit behaviour.

Fixes: 90634e85

 ("PCI: rcar: Convert PCI scan API to pci_scan_root_bus_bridge()")
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Harunobu Kurokawa <harunobu.kurokawa.dn@renesas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>