Allow radio to modify net.ppp* properties for dns

The radio bringup script was changed from operating as root to operating as radio.  This is
preventing it from adding the "net.ppp0.dns0" and "net.ppp0.dns1" properties that
ConnectivityService needs to correctly set dns.

bug: 2077628

init/property_service.c

@@ -55,6 +55,7 @@ struct {
 } property_perms[] = {
     { "net.rmnet0.",    AID_RADIO },
     { "net.gprs.",      AID_RADIO },
+    { "net.ppp",        AID_RADIO },
     { "ril.",           AID_RADIO },
     { "gsm.",           AID_RADIO },
     { "net.dns",        AID_RADIO },