fuchsia: fix regression in fmt::Debug for Events (#699)

diff --git a/src/sys/fuchsia/selector.rs b/src/sys/fuchsia/selector.rs
index 748d669..caba672 100644
--- a/src/sys/fuchsia/selector.rs
+++ b/src/sys/fuchsia/selector.rs
@@ -349,7 +349,7 @@
 impl fmt::Debug for Events {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_struct("Events")
-            .field("len", self.len())
+            .field("len", &self.len())
             .finish()
     }
 }