fix the docs preview version number

Change-Id: I8c8a8fb6bd431eade40e62a6b135b628811c0558
diff --git a/Android.mk b/Android.mk
index 3f0dad1..74cf4ee 100644
--- a/Android.mk
+++ b/Android.mk
@@ -871,10 +871,10 @@
 
 framework_docs_LOCAL_DROIDDOC_OPTIONS += \
 		-hdf sdk.codename N \
-		-hdf sdk.preview.version 1 \
+		-hdf sdk.preview.version 2 \
 		-hdf sdk.version $(framework_docs_SDK_VERSION) \
 		-hdf sdk.rel.id $(framework_docs_SDK_REL_ID) \
-		-hdf sdk.preview 2
+		-hdf sdk.preview 1
 
 # ====  the api stubs and current.xml ===========================
 include $(CLEAR_VARS)