Staging: comedi: remove MACRO pr_fmt in unioxx5.c

This patch removes MACRO definition pr_fmt which was initially
required by pr_info and pr_err logging functions.

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>