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>

arch/powerpc/kvm/book3s_hv.c

@@ -2831,7 +2831,6 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
 		 */
 		if (!thr0_done)
 			kvmppc_start_thread(NULL, pvc);
-		thr += pvc->num_threads;
 	}
 
 	/*