fat: fix crash with big sector size

Apple iPod nanos have sector sizes of 2 or 4 KiB, which crashes U-Boot when it
tries to read the boot sector into 512-byte buffer situated on stack. Make the
FAT code indifferent to the sector size.

Signed-off-by: Sergei Shtylyov <sshtylyov@mvista.com>
2 files changed