Fix Const-Correctness for RIL_RadioFunctions

Re-add constant for function pointer table to
RIL_RadioFunctions. Const was accidentally removed
during a warnings cleanup.

Bug: 64231560
Test: compilation
Change-Id: I93675980c51d9162f624495d12fe3c97f1da8031
diff --git a/libril/sap_service.h b/libril/sap_service.h
index afed612..cb5ae10 100644
--- a/libril/sap_service.h
+++ b/libril/sap_service.h
@@ -24,10 +24,10 @@
 
 namespace sap {
 
-void registerService(RIL_RadioFunctions *callbacks);
+void registerService(const RIL_RadioFunctions *callbacks);
 void processResponse(MsgHeader *rsp, RilSapSocket *sapSocket);
 void processUnsolResponse(MsgHeader *rsp, RilSapSocket *sapSocket);
 
 }   // namespace android
 
-#endif  // RIL_SERVICE_H
\ No newline at end of file
+#endif  // RIL_SERVICE_H