powerpc/powernv: Detach from PE on releasing PCI device

The PCI hotplug can be part of EEH error recovery. The @pdn and
the device's PE number aren't removed and added afterwords. The
PE number in @pdn should be set to an invalid one. Otherwise, the
PE's device count is decreased on removing devices while failing
to be increased on adding devices. It leads to unbalanced PE's
device count and make normal PCI hotplug path broken.

Fixes: c5f7700b

 ("powerpc/powernv: Dynamically release PE")
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>