staging: comedi: replace printk calls in comedi core

Replace the printk() calls in the comedi core module with something more
suitable, such as dev_...() or pr_...().  Remove the ones that report a
failure to increment a module count (try_module_get() failure).  Change
the printk() call in the DPRINTK() macro to pr_debug().

TODO: Most of the DPRINTK() calls need to be replaced with something
else.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>