trace: Break on RBP OVERFLOW

There's not point in continuing the loop once this occurs. It just
results in printing 'RBP OVERFLOW' repeatedly.

src/arch/x86_64/interrupt/trace.rs

@@ -30,6 +30,7 @@ pub unsafe fn stack_trace() {
             }
         } else {
             println!("  {:>016X}: RBP OVERFLOW", rbp);
+            break;
         }
     }
 }