staging: comedi: ni_tio: tidy up ni_tio_init_counter()

This function is called to initialize/reset a gpct counter during a
comedi drivers (*attach).

For aesthetics, move this exported function toward the end of the file.

Tidy up the functions a bit by just open coding the '0x0' values used
to initialize some of the registers.

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>