fix meat pack internal buffer for multi serial

Marlin/src/gcode/queue.cpp

   LOOP_L_N(p, NUM_SERIAL)
     if (serial_data_available(p))
       return true;
+  return false;
 }
 
 inline int read_serial(const serial_index_t index) { return SERIAL_IMPL.read(index); }

Marlin/src/gcode/sd/M28_M29.cpp

     // Binary transfer mode
     if ((card.flag.binary_mode = binary_mode)) {
       SERIAL_ECHO_MSG("Switching to Binary Protocol");
-      TERN_(HAS_MULTI_SERIAL, card.transfer_port_index = queue.ring_buffer.command_port());
+      TERN_(HAS_MULTI_SERIAL, card.transfer_port_index = queue.ring_buffer.command_port().index);
     }
     else
       card.openFileWrite(p);