parisc: Fix return code of pdc_iodc_print()

commit 5d1335da upstream.

There is an off-by-one if the printed string includes a new-line
char.

Cc: stable@vger.kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>