staging: comedi: ni_labpc: fix 8254 timer programming

As pointed out by Ian Abbott, the i8254_load() function does not
use the I8254_MODE* values to specify the "mode".

The labpc_counter_load() function in this driver is passed an
I8254_MODE* value so we need to use the i8254_set_mode() and
i8254_write() helpers instead of i8254_load() to program the
timers.

The calls to labpc_counter_load() will not fail so change the
return to void and remove all the unnecessary error handling.

Similarly, change the return type of labpc_counter_set_mode() to
void and remove the unnecessary error handling.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>