[coreboot] lar directory handling

[Myles Watson]

This is a simple patch which corrects directory handling for add
(makes it the same as create.)

Without this patch you can create a lar and recursively add a
directory to it, but you can't add one with add.

Another patch might be to make lar -l print something when you use the
directory option, but I'm not sure what was intended originally.

Myles

Signed-off-by: Myles Watson