Refactor location of DefaultAffinity().

Change-Id: I5fbebefb6db8fc2b65da0e4d87f5d7ed8c759918
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/events/event_loop.h b/aos/events/event_loop.h
index 9ad9f4f..68b5b35 100644
--- a/aos/events/event_loop.h
+++ b/aos/events/event_loop.h
@@ -724,13 +724,7 @@
   // Defaults to 0 if this loop will not run realtime.
   virtual int runtime_realtime_priority() const = 0;
 
-  static cpu_set_t DefaultAffinity() {
-    cpu_set_t result;
-    for (int i = 0; i < CPU_SETSIZE; ++i) {
-      CPU_SET(i, &result);
-    }
-    return result;
-  }
+  static cpu_set_t DefaultAffinity();
 
   // Sets the scheduler affinity to run the event loop with. This may only be
   // called before Run().