added carry and divz checks across the fat32 code

also use the pointers we have in bss to our saved data

include/error_codes.inc

@@ -60,9 +60,9 @@
 %define STAGE2_FAT32_INIT_ERROR      'H'
 %define STAGE2_FAT32_NO_FILE         'I'
 %define STAGE2_FAT32_END_OF_CHAIN    'J'
-%define STAGE2_ERROR_RESERVED_K      'K'
-%define STAGE2_ERROR_RESERVED_L      'L'
-%define STAGE2_ERROR_RESERVED_M      'M'
+%define STAGE2_FAT32_NCLUS_CFDIVZ    'K'
+%define STAGE2_FAT32_CLS2LBA_CF      'L'
+%define STAGE2_FAT32_INIT_CF         'M'
 %define STAGE2_ERROR_RESERVED_N      'N'
 %define STAGE2_ERROR_RESERVED_O      'O'
 %define STAGE2_ERROR_RESERVED_P      'P'