According to PPC440 User Manual PPC440 has multiple opcodes for icbt
instruction: one for compatibility with older cores and two 440
specific opcodes one of which is defined in BookE. QEMU only
implements two of these, add the missing one.
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>