Support for booting from eMMC

Fusee will Look for FAT32 partition on BOOT1 (1MB offset), BOOT1, GPP, SD, in this order
If a .no_boot_storage file is found in the root directory, the partition is skipped

fusee/program/source/fatfs/diskio.h

@@ -25,6 +25,8 @@ typedef enum {
 typedef enum {
     DRIVE_SD,
     DRIVE_SYS,
+    DRIVE_BOOT1,
+    DRIVE_BOOT1_OFF,
 } DDRIVE;