powerpc/eeh: Do not invalidate PE properly

While the EEH does recovery on the specific PE that has PCI errors,
the PCI devices belonging to the PE will be removed and the PE will
be marked as invalid since we still need the information stored in
the PE. We only invalidate the PE when it doesn't have associated
EEH devices and valid child PEs. However, the code used to check
that is wrong. The patch fixes that.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>