Document new QEMU pipe implementation.

+ Rename android/pipe-net.c to android/hw-pipe-net.c

Change-Id: Ia2e2466c3bf3ea812f36639420fad7ce2e0cb61d
diff --git a/vl-android.c b/vl-android.c
index abfa423..e151cc0 100644
--- a/vl-android.c
+++ b/vl-android.c
@@ -51,8 +51,9 @@
 #include "charpipe.h"
 #include "modem_driver.h"
 #include "android/gps.h"
-#include "android/hw-qemud.h"
 #include "android/hw-kmsg.h"
+#include "android/hw-pipe-net.h"
+#include "android/hw-qemud.h"
 #include "android/charmap.h"
 #include "android/globals.h"
 #include "android/utils/bufprint.h"
@@ -63,7 +64,6 @@
 #include "android/utils/tempfile.h"
 #include "android/display-core.h"
 #include "android/utils/timezone.h"
-#include "android/pipe-net.h"
 #include "android/snapshot.h"
 #include "targphys.h"
 #include "tcpdump.h"