KVM: PPC: Book3S HV: Remove useless statement

This removes a statement that has no effect.  It should have been
removed in commit 898b25b2

 ("KVM: PPC: Book3S HV: Simplify dynamic
micro-threading code", 2017-06-22) along with the loop over the
piggy-backed virtual cores.

This issue was reported by Coverity.

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