gta4xl-common: Switch back to non-threaded skiagl renderengine

* On T skiaglthreaded (the default renderengine since S) causes
  the first few frames of the bootanimation to lag badly,
  on lineage resulting in an seemingly "delayed" bootanimation
  since the first few frames are pure black

Change-Id: I8355d98ae5c8c2406cb79912eec50f41fcf756dd
diff --git a/vendor.prop b/vendor.prop
index 929eff1..9feaf73 100644
--- a/vendor.prop
+++ b/vendor.prop
@@ -33,6 +33,7 @@
 ro.frp.pst=/dev/block/persistent
 
 ## Graphics
+debug.renderengine.backend=skiagl
 debug.sf.latch_unsignaled=1
 ro.opengles.version=196610
 ro.surface_flinger.max_frame_buffer_acquired_buffers=3