scanlog.c is only compiled on pSeries.  Thus, this patch moves it to
platforms/pseries.

Built and booted on pSeries LPAR (ARCH=powerpc and ARCH=ppc64).  Built
for iSeries (ARCH=powerpc).
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NPaul Mackerras <paulus@samba.org>