target-ppc: Remove unused power_mode field from cpu state

CPUPPCState includes a variable 'power_mode' which is used nowhere.  This
patch removes it.  This includes saving a dummy zero in its place during
vmsave, to avoid breaking the save format.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/target-ppc/machine.c b/target-ppc/machine.c
index d6c2ee4..21ce757 100644
--- a/target-ppc/machine.c
+++ b/target-ppc/machine.c
@@ -82,7 +82,7 @@
     qemu_put_betls(f, &env->hflags);
     qemu_put_betls(f, &env->hflags_nmsr);
     qemu_put_sbe32s(f, &env->mmu_idx);
-    qemu_put_sbe32s(f, &env->power_mode);
+    qemu_put_sbe32(f, 0);
 }
 
 int cpu_load(QEMUFile *f, void *opaque, int version_id)
@@ -167,7 +167,7 @@
     qemu_get_betls(f, &env->hflags);
     qemu_get_betls(f, &env->hflags_nmsr);
     qemu_get_sbe32s(f, &env->mmu_idx);
-    qemu_get_sbe32s(f, &env->power_mode);
+    qemu_get_sbe32(f); /* Discard unused power_mode */
 
     return 0;
 }