PCI/ACPI: Fix pci_acpi_preserve_config() memory leak

pci_acpi_preserve_config() leaks memory by returning early without freeing
the ACPI object on success. Fix that by always freeing the obj, which is
not needed by the caller.

Fixes: 9d7d5db8 ("PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to pci_register_host_bridge()")
Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250825214642.142135-1-nirmoyd@nvidia.com