Move source prop files for docs/platforms/usb driver back into dev.

Change-Id: I4632dc69432b720d586c84834f89c843a2eaf5cd
diff --git a/sdk/platform_source.properties b/sdk/platform_source.properties
new file mode 100644
index 0000000..d4ff795
--- /dev/null
+++ b/sdk/platform_source.properties
@@ -0,0 +1,5 @@
+Pkg.Desc=Android SDK Platform 2.1_r1
+Pkg.UserSrc=false
+Platform.Version=2.1
+Pkg.Revision=1
+AndroidVersion.ApiLevel=7