prop: add prop for google  assistant

Change-Id: Ica24a4f6907b00c9e74565ebcd82d1ffd87640d4
diff --git a/config/common.mk b/config/common.mk
index a03815c..8e42f13 100644
--- a/config/common.mk
+++ b/config/common.mk
@@ -25,6 +25,10 @@
     ro.build.selinux=1 \
     persist.sys.disable_rescue=true
 
+# Google assistant
+PRODUCT_SYSTEM_DEFAULT_PROPERTIES += \
+    ro.opa.eligible_device=true
+
 # Tethering - allow without requiring a provisioning app
 # (for devices that check this)
 PRODUCT_SYSTEM_DEFAULT_PROPERTIES += \