target/ppc: Prevent supervisor from modifying MSR[ME]

Prevent guest state modifying the MSR[ME] bit. Per ISA:

  An attempt to modify MSR[ME] in privileged but non-hypervisor state
  is ignored (i.e., the bit is not changed).

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
1 file changed