edtlib: Exclude PCI devices from some inapplicable checks

PCI devices are have some differences to regular nodes:
* node name specifies device/function e.g. "pcie@1,0"
* register address has a different meaning
* zero-sized register is allowed

This improves alignment with Linux DT for PCI devices

Signed-off-by: Grant Ramsay <gramsay@enphaseenergy.com>