A new fatbuf was allocated by get_fs_info() (called by fat_itr_root()),
but not freed, resulting in eventually running out of memory. Spotted
by running 'ls -r' in a large FAT filesystem from Shell.efi.
fatbuf is mainly used to cache FAT entry lookups (get_fatent())..
possibly once fat_write.c it can move into the iterator to simplify
this.
Signed-off-by: Rob Clark <robdclark@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org> Reviewed-by: Ćukasz Majewski <lukma@denx.de>