Reenable some supressed warnings for the objc SDK.

Bug: webrtc:8441
Change-Id: I6b427dfc1fe275e274d042766e0850628cf19994
Reviewed-on: https://webrtc-review.googlesource.com/15000
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20425}
diff --git a/p2p/base/port.h b/p2p/base/port.h
index 61fd750..9e5c223 100644
--- a/p2p/base/port.h
+++ b/p2p/base/port.h
@@ -432,7 +432,7 @@
   // A virtual cost perceived by the user, usually based on the network type
   // (WiFi. vs. Cellular). It takes precedence over the priority when
   // comparing two connections.
-  uint16_t network_cost_;
+  int16_t network_cost_;
   State state_ = State::INIT;
   int64_t last_time_all_connections_removed_ = 0;