Stepper and Endstops as singleton objects

Marlin/cardreader.cpp

@@ -596,7 +596,7 @@ void CardReader::updir() {
 }
 
 void CardReader::printingHasFinished() {
-  st_synchronize();
+  stepper.synchronize();
   if (file_subcall_ctr > 0) { // Heading up to a parent file that called current as a procedure.
     file.close();
     file_subcall_ctr--;