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 <[e-mail]>
Acked-by: Scott Wood <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/kvm/e500.c

···
                            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;