Fixes a number of these errors:
cc1: warnings being treated as errors
fsys_fat.c: In function 'fat_dir':
fsys_fat.c:304: warning: array subscript has type 'char'
Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
These ugly casts are needed according to the ISO C spec.
Acked-by: Keir Fraser <keir@xensource.com>