Staging: adis16255: Fix compile error

This patch solves a compilation error in today linux-next tree.

The adis16255 staging driver Makefile seems to be wrong. I think this patch solves the issue.

Signed-off-by: Javier Martinez Canillas <martinez.javier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>