msm8974-common: Use threaded GLES render engine

In Android 12, the default graphics engine is no longer GLES.

For msm8974, the OS crashes if skia is used and never boots.

system.prop

@@ -20,6 +20,9 @@ debug.hwui.use_buffer_age=false
 debug.sf.disable_backpressure=1
 debug.sf.latch_unsignaled=1
 
+# Graphics
+debug.renderengine.backend=threaded
+
 # Memory optimizations
 ro.vendor.qti.sys.fw.bservice_enable=true