Make CardReader class static (#12451)

* Make CardReader a static class
* Make CardReader flags into bitfields

Marlin/src/HAL/HAL_LPC1768/main.cpp

@@ -106,7 +106,7 @@ void HAL_idletask(void) {
     // the disk if Marlin has it mounted. Unfortuately there is currently no way
     // to unmount the disk from the LCD menu.
     // if (IS_SD_PRINTING() || IS_SD_FILE_OPEN())
-    if (card.cardOK)
+    if (card.flag.cardOK)
       MSC_Aquire_Lock();
     else
       MSC_Release_Lock();