[FREELDR] Use RtlStringCbPrintfA instead of sprintf

[FREELDR] Use RtlStringCbPrintfA instead of sprintf

Fixes GCC 8 warnings like:
boot/freeldr/freeldr/disk/scsiport.c:806:31: error: 'partition(0)' directive writing 12 bytes into a region of size between 1 and 64 [-Werror=format-overflow=]
     sprintf(PartitionName, "%spartition(0)", ArcName);
                               ^~~~~~~~~~~~
boot/freeldr/freeldr/disk/scsiport.c:806:5: note: 'sprintf' output between 13 and 76 bytes into a destination of size 64
     sprintf(PartitionName, "%spartition(0)", ArcName);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~