Staging: comedi: change printk to dev_err/dev_dbg in unioxx5.c

This is a patch which fixes coding style issues due to printk usage in
unioxx5.c found by checkpatch.pl in the following functions:
1) __unioxx5_digital_read
2) __unioxx5_analog_read
3) __unioxx5_digital_config

To subsitute printk with dev_err/dev_dbg, access to the struct device is
required. The function definitions of the above functions have been changed
to take the pointer to the struct comedi_subdevice as a parameter instead
of the pointer to struct unioxx5_subd_priv.

The pointers to the stuct device and the struct unioxx5_subd_priv are
obtained through the pointer to the struct comedi_subdevice in these functions.

The function calls of __unioxx5_digital_read and __unioxx5_analog_read in
unioxx5_subdev_read have been changed to pass the pointer to the struct
comedi_subdevice.

Signed-off-by: Conrad Gomes <conrad.s.j.gomes@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>