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.cpp b/libril/sap_service.cpp
index 7bed05a..1f6fe54 100644
--- a/libril/sap_service.cpp
+++ b/libril/sap_service.cpp
@@ -915,7 +915,7 @@
     processResponse(rsp, sapSocket, MsgType_UNSOL_RESPONSE);
 }
 
-void sap::registerService(RIL_RadioFunctions *callbacks) {
+void sap::registerService(const RIL_RadioFunctions *callbacks) {
     using namespace android::hardware;
     int simCount = 1;
     const char *serviceNames[] = {