Merge remote-tracking branch 'remotes/powerpc/topic/ppc-kvm' into kvm-ppc-next

This merges in the ppc-kvm topic branch of the powerpc tree to get the
commit that reverts the patch "KVM: PPC: Book3S HV: POWER9 does not
require secondary thread management".  This is needed for subsequent
patches which will be applied on this branch.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>