Replace use of uninitialized variable with the PCI device number
in an error message as this is what we use elsewhere to derive
the PCIe port number. Use ofnode_read_pci_addr() to read the
PCI address of the node and derive the device number from that.
Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reported-by: Andrew Goodbody <andrew.goodbody@linaro.org>