made sd code only compile with SDSUPPORT defined. safes 10k of codespace

Marlin/SdVolume.h

@@ -17,6 +17,8 @@
  * along with the Arduino SdFat Library.  If not, see
  * <http://www.gnu.org/licenses/>.
  */
+#include "Marlin.h"
+#ifdef SDSUPPORT
 #ifndef SdVolume_h
 #define SdVolume_h
 /**
@@ -209,3 +211,4 @@ class SdVolume {
 #endif  // ALLOW_DEPRECATED_FUNCTIONS
 };
 #endif  // SdVolume
+#endif