Make android_net_NetUtils include what it actually uses.

Bug: http://b/28519060
Change-Id: I49dcd358d3fc8e0ba5c5e0b50a0f5dcc63281d22
diff --git a/core/jni/android_net_NetUtils.cpp b/core/jni/android_net_NetUtils.cpp
index ba0876d..c104658 100644
--- a/core/jni/android_net_NetUtils.cpp
+++ b/core/jni/android_net_NetUtils.cpp
@@ -25,10 +25,7 @@
 #include <arpa/inet.h>
 #include <net/if.h>
 #include <linux/filter.h>
-#include <linux/if.h>
-#include <linux/if_ether.h>
-#include <linux/if_packet.h>
-#include <net/if_ether.h>
+#include <netinet/ether.h>
 #include <netinet/ip.h>
 #include <netinet/udp.h>
 #include <cutils/properties.h>