Add HAS_MULTI_SERIAL conditional

Marlin/src/gcode/sd/M28_M29.cpp

@@ -27,7 +27,7 @@
 #include "../gcode.h"
 #include "../../sd/cardreader.h"
 
-#if NUM_SERIAL > 1
+#if HAS_MULTI_SERIAL
   #include "../queue.h"
 #endif
 
@@ -49,9 +49,7 @@ void GcodeSuite::M28() {
     // Binary transfer mode
     if ((card.flag.binary_mode = binary_mode)) {
       SERIAL_ECHO_MSG("Switching to Binary Protocol");
-      #if NUM_SERIAL > 1
-        card.transfer_port_index = queue.port[queue.index_r];
-      #endif
+      TERN_(HAS_MULTI_SERIAL, card.transfer_port_index = queue.port[queue.index_r]);
     }
     else
       card.openFileWrite(p);