Allow radio to set sys.usb.config

This allows the ril to put the phone into diagnostic mode

Change-Id: Iafc8164991550e7ab0ffda8b8da1d58e34a4225b
diff --git a/init/property_service.c b/init/property_service.c
index dd61b1b..18231e8 100644
--- a/init/property_service.c
+++ b/init/property_service.c
@@ -68,6 +68,7 @@
     { "gsm.",             AID_RADIO,    0 },
     { "persist.radio",    AID_RADIO,    0 },
     { "net.dns",          AID_RADIO,    0 },
+    { "sys.usb.config",   AID_RADIO,    0 },
     { "net.",             AID_SYSTEM,   0 },
     { "dev.",             AID_SYSTEM,   0 },
     { "runtime.",         AID_SYSTEM,   0 },