core/hostservices.c and core/slw.c: cleanup log messages

printing timebase is redundant, prlog does that for us.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>