staging: comedi: ni_660x: init TIO chips before subdevice init

For aesthetics, initialize the TIO chips before the subdevices are
allocated and initialized.

Refactor the function to initialize all the TIO chips and move it
to a better place in the driver.

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>