libhwc2on1adapter: Move to vendor partition

libhwc2on1adapter is a shim layer for legacy hwcomposer HALs.  This is
only used by android.hardware.graphics.composer@2.1-impl.so.  This must
not be accessed by framework modules.  Thus, this commit moves
libhwc2on1adapter to the vendor partition and removes vendor_available.

Bug: 38302528
Test: Sailfish builds and boots.
Change-Id: I43d66c8c62f3dc90e75805f6a459573c093f9f14
diff --git a/libs/hwc2on1adapter/Android.bp b/libs/hwc2on1adapter/Android.bp
index 5d7f660..ec9cbf8 100644
--- a/libs/hwc2on1adapter/Android.bp
+++ b/libs/hwc2on1adapter/Android.bp
@@ -14,7 +14,7 @@
 
 cc_library_shared {
     name: "libhwc2on1adapter",
-    vendor_available: true,
+    vendor: true,
 
     clang: true,
     cppflags: [