shill: vpn: Move vpn 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=`USE='vpn' FEATURES=test emerge-$BOARD shill`
TEST=`USE='vpn clang asan' FEATURES=test emerge-$BOARD shill`

Change-Id: I02d23511a80655098d50e248321c77d23f8caaa9
Reviewed-on: https://chromium-review.googlesource.com/229870
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
diff --git a/device_info.cc b/device_info.cc
index 4e8e6c0..6350bc6 100644
--- a/device_info.cc
+++ b/device_info.cc
@@ -47,7 +47,7 @@
 #include "shill/routing_table.h"
 #include "shill/service.h"
 #include "shill/virtio_ethernet.h"
-#include "shill/vpn_provider.h"
+#include "shill/vpn/vpn_provider.h"
 #include "shill/wifi.h"
 
 using base::Bind;