KVM: PPC: e500: fix handling local_sid_lookup result

The function can return negative value.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kvm/e500.c b/arch/powerpc/kvm/e500.c
index b29ce75..32fdab5 100644
--- a/arch/powerpc/kvm/e500.c
+++ b/arch/powerpc/kvm/e500.c
@@ -237,7 +237,8 @@
                            struct kvm_book3e_206_tlb_entry *gtlbe)
 {
 	struct vcpu_id_table *idt = vcpu_e500->idt;
-	unsigned int pr, tid, ts, pid;
+	unsigned int pr, tid, ts;
+	int pid;
 	u32 val, eaddr;
 	unsigned long flags;