staging: comedi: ni_6527: convert printk() to dev_...()

Convert the `printk()` calls in this drivers to use the `dev_...()`
calls instead.  Remove the initial `printk()` call in the comedi
`attach()` handler (`ni6527_attach()`) as it's a bit redundant - the
board type and contents of a board ID register are printed later in the
function.

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>