staging: comedi: ni_660x: convert printk() to dev_...()

Convert the `printk()` calls in this drivers to use the `dev_...()`
calls instead.  Replace some `printk()` calls in the comedi `attach()`
handler (`ni_660x_attach()`) with a single `dev_info()` at the end.
Remove some `printk()` calls before `BUG()` calls.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>