*spapr_pci: dump _FDT() error messages

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*spapr_pci: add drc_entry lists for PHBs

Reserve 32 entries for SLOT type in each PHB's initial FDT. This is
necessary for allowing hotplugging of devices to it later.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*spapr_pci: stash

Changes are a pretty tangled, committing changes as a stash for now.

- s/struct drc_entry/DrcEntry/ as per coding guidelines
- add 'child_entries' field to DrcEntry's to handle entries for each
  PHB
- rework hotplug path to attach FDT node directly to corresponding
  DrcEntry->ConfigureConnectorState field. Can probably drop all the
  code that was added to store/search the entire SPAPR DT.

With these changes in place we can now successfully pass a DT to a
guest via `drmgr -c slot -s "Slot xx" -a`.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>