[binder] Replace NULL/0 with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

clang-tidy -checks=modernize-use-nullptr -p compile_commands.json -fix
...

Test: m
Bug: 68236239
Change-Id: I3181bc5683796423a98b0f9b94daf30880c07bdc
diff --git a/libs/binder/IAppOpsService.cpp b/libs/binder/IAppOpsService.cpp
index 9c76350..068664b 100644
--- a/libs/binder/IAppOpsService.cpp
+++ b/libs/binder/IAppOpsService.cpp
@@ -109,7 +109,7 @@
         data.writeStrongBinder(clientToken);
         remote()->transact(GET_TOKEN_TRANSACTION, data, &reply);
         // fail on exception
-        if (reply.readExceptionCode() != 0) return NULL;
+        if (reply.readExceptionCode() != 0) return nullptr;
         return reply.readStrongBinder();
     }