powerpc/pseries: The RPA PCI hotplug driver depends on EEH

The RPA PCI hotplug driver calls EEH routines, so should depend on
EEH. Also PPC_PSERIES implies PPC64, so remove that.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>