spapr: fix bogus function name in comment

$ git grep spapr_ppc_reset
hw/ppc/spapr.c: * as part of spapr_ppc_reset().

$ git grep ppc_spapr_reset
hw/ppc/spapr.c:static void ppc_spapr_reset(void)
hw/ppc/spapr.c:    mc->reset = ppc_spapr_reset;
hw/ppc/spapr_hcall.c:        /* If ppc_spapr_reset() did not set up a HPT
 but one is necessary

Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>