powerpc/pci: Remove dead checks for CONFIG_PPC_OF

PPC_OF is always selected for arch/powerpc.  This patch removes the stale
#defines

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>