comedi: drivers: ni_tio: Fix slightly broken kernel-doc and demote others

Fixes the following W=1 kernel build warning(s):

 drivers/staging/comedi/drivers/ni_tio.c:1515: warning: Function parameter or member 'counter_dev' not described in 'ni_tio_get_routing'
 drivers/staging/comedi/drivers/ni_tio.c:1515: warning: Function parameter or member 'dest' not described in 'ni_tio_get_routing'
 drivers/staging/comedi/drivers/ni_tio.c:1515: warning: expecting prototype for Retrieves the register value of the current source of the output selector for(). Prototype was for ni_tio_get_routing() instead
 drivers/staging/comedi/drivers/ni_tio.c:1544: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/staging/comedi/drivers/ni_tio.c:1584: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mori Hess <fmhess@users.sourceforge.net>
Cc: "J.P. Mellor" <jpmellor@rose-hulman.edu>
Cc: Herman.Bruyninckx@mech.kuleuven.ac.be
Cc: Wim.Meeussen@mech.kuleuven.ac.be
Cc: Klaas.Gadeyne@mech.kuleuven.ac.be
Cc: Comedi <comedi@comedi.org>
Cc: linux-staging@lists.linux.dev
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210520122538.3470259-4-lee.jones@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>