wallpaper: add missing @hides

Add missing @hides to setWallpaperOverscroll and setWallpaperOverscrollOffsets

Change-Id: I1cfe876272d7c0a94bef122567da30318eac9400
(cherry picked from commit 5d230672e15d25a5136c604774da9b3550a19711)

Conflicts:
	core/java/android/app/WallpaperManager.java