shill: wifi: Move wifi code to its own sub-directory.

This CL is part of a series of CLs, which aim to reorganzie shill's flat
source code structure into a more modular form by moving technology
specific code into their own sub-directories.

BUG=chromium:433419
TEST=`FEATURES=test emerge-$BOARD shill`
TEST=`USE='clang asan' FEATURES=test emerge-$BOARD shill`

Change-Id: Ic6bf64e7fe263fd0b2277877d78cf776f179e7d7
Reviewed-on: https://chromium-review.googlesource.com/230460
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
diff --git a/shill_daemon.cc b/shill_daemon.cc
index c65bd53..27662dd 100644
--- a/shill_daemon.cc
+++ b/shill_daemon.cc
@@ -8,7 +8,6 @@
 
 #include <base/bind.h>
 
-#include "shill/callback80211_metrics.h"
 #include "shill/dhcp_provider.h"
 #include "shill/diagnostics_reporter.h"
 #include "shill/error.h"
@@ -19,6 +18,7 @@
 #include "shill/proxy_factory.h"
 #include "shill/routing_table.h"
 #include "shill/shill_config.h"
+#include "shill/wifi/callback80211_metrics.h"
 
 using base::Bind;
 using base::Unretained;