KVM: PPC: Fix compile error in e500_tlb.c

The e500_tlb.c file didn't compile for me due to the following error:

arch/powerpc/kvm/e500_tlb.c: In function ‘kvmppc_e500_shadow_map’:
arch/powerpc/kvm/e500_tlb.c:300: error: format ‘%lx’ expects type ‘long unsigned int’, but argument 2 has type ‘gfn_t’

So let's explicitly cast the argument to make printk happy.
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/e500_tlb.c

@@ -297,7 +297,8 @@ static inline void kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 	/* Get reference to new page. */
 	new_page = gfn_to_page(vcpu_e500->vcpu.kvm, gfn);
 	if (is_error_page(new_page)) {
-		printk(KERN_ERR "Couldn't get guest page for gfn %lx!\n", gfn);
+		printk(KERN_ERR "Couldn't get guest page for gfn %lx!\n",
+				(long)gfn);
 		kvm_release_page_clean(new_page);
 		return;
 	}