pci-dt-slot: Big ol' cleanup
pci-dt-slot: Big ol' cleanup

The underlying data that we get from HDAT can only really describe a
PCIe system. As such we can simplify the devicetree slot lookup code
by only caring about the important cases, namly, root ports and switch
downstream ports.

This also fixes a bug where root port didn't get a Slot label applied
which results in devices under that port not having ibm,loc-code set.
This results in the EEH core being unable to report the location of
EEHed devices under that port.

Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

shenki/skiboot,legoater/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,qemu/skiboot,stewart-ibm/skiboot,open-power/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,stewart-ibm/skiboot,shenki/skiboot,stewart-ibm/skiboot,shenki/skiboot,qemu/skiboot,qemu/skiboot