ppc/prep: update MAINTAINERS file

Signed-off-by: NHervé Poussineau <hpoussin@reactos.org>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

MAINTAINERS

@@ -671,10 +671,13 @@ F: hw/misc/macio/
 F: hw/intc/heathrow_pic.c
 
 PReP
+M: Hervé Poussineau <hpoussin@reactos.org>
 L: qemu-devel@nongnu.org
 L: qemu-ppc@nongnu.org
-S: Odd Fixes
+S: Maintained
 F: hw/ppc/prep.c
+F: hw/ppc/prep_systemio.c
+F: hw/ppc/rs6000_mc.c
 F: hw/pci-host/prep.[hc]
 F: hw/isa/pc87312.[hc]
 F: pc-bios/ppc_rom.bin