powerpc: iSeries build fixes

log_plpar_hcall_return is only used on PPC_PSERIES, so move
it closer to its users and inside ifdef CONFIG_PPC_PSERIES.

remove the last vestiges of systemcfg in iSeries.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --cc arch/powerpc/kernel/lparcfg.c
Simple merge

diff --cc arch/powerpc/platforms/iseries/setup.c
Simple merge