KVM: PPC: fix build warning in kvm_arch_vcpu_ioctl_run

Fix compile warning:
  CC [M]  arch/powerpc/kvm/powerpc.o
  arch/powerpc/kvm/powerpc.c: In function 'kvm_arch_vcpu_ioctl_run':
  arch/powerpc/kvm/powerpc.c:290: warning: 'gpr' may be used uninitialized in this function
  arch/powerpc/kvm/powerpc.c:290: note: 'gpr' was declared here
Signed-off-by: Denis Kirjanov <dkirjanov@kernel.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/powerpc/kvm/powerpc.c

@@ -287,7 +287,7 @@ static void kvmppc_complete_dcr_load(struct kvm_vcpu *vcpu,
 static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
                                       struct kvm_run *run)
 {
-	u64 gpr;
+	u64 uninitialized_var(gpr);
 
 	if (run->mmio.len > sizeof(gpr)) {
 		printk(KERN_ERR "bad MMIO length: %d\n", run->mmio.len);