target/ppc: Drop cases for unimplemented MPC8xx MMU

target/ppc: Drop cases for unimplemented MPC8xx MMU

Drop MPC8xx cases from get_physical_address_wtlb() and ppc_jumbo_xlate().
The default case would still catch this and abort the same way and
there is still a warning about it in ppc_tlb_invalidate_all() which is
called in ppc_cpu_reset_hold() so likely we never get here but to make
sure add a case to ppc_xlate() to the same effect.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>