um: Add BUG() to do_ops()'s error path

In case we encounter a bad operation in do_ops() something is really
broken and it's better to BUG().

Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index 7f3d4d86..f819af9 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -75,6 +75,7 @@
 		default:
 			printk(KERN_ERR "Unknown op type %d in do_ops\n",
 			       op->type);
+			BUG();
 			break;
 		}
 	}