[ARM] 3355/1: NSLU2: remove propmt depends

Patch from Alessandro Zummo

The patch that would have made the NSLU2
kernel non compatible with other ixp4xx machs
never entered the kernel. So it is actually
safe to remove the prompt dependencies.

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>