PNP: remove null pointer checks

Remove some null pointer checks.  Null pointers in these areas indicate
programming errors, and I think it's better to oops immediately rather
than return an error that is easily ignored.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Adam Belay <abelay@novell.com>
Signed-off-by: Len Brown <len.brown@intel.com>