On systems with PCI_PROBE_ONLY set, we rely on BAR assignments from
firmware. Previously we did not insert those resources into the resource
tree, so we had to skip pci_enable_resources() because it fails if
resources are not in the resource tree.
Now that we *do* insert resources even when PCI_PROBE_ONLY is set, we no
longer need the ARM64-specific pcibios_enable_device(). Remove it so we
use the generic version.