update platform version number for docs

Change-Id: If0866ab1544ce0f5e70bbbe93d30ed27c4403406
diff --git a/Android.mk b/Android.mk
index ae03d6c..24c0dc4 100644
--- a/Android.mk
+++ b/Android.mk
@@ -453,7 +453,7 @@
 
 ## SDK version identifiers used in the published docs
   # major[.minor] version for current SDK. (full releases only)
-framework_docs_SDK_VERSION:=3.0
+framework_docs_SDK_VERSION:=3.1
   # release version (ie "Release x")  (full releases only)
 framework_docs_SDK_REL_ID:=1