Fix my own merge stupidity

Way back in August I merged Heiko's patch:
566a494f: [PCS440EP] upgrade the PCS440EP board

with Jon's CONFIG_COMMANDS patches.

This was done in commit: 6bf6f114

However, in the process, I left out some of Heiko's good changes.

Now Heiko's and Jon's patches are properly merged in fat_register_device()

Signed-off-by: Andy Fleming <afleming@freescale.com>