staging: comedi: amplc_pci224: remove pci224_cascade_ns_to_timer()

This function is just a wrapper around i8253_cascade_ns_to_timer().
Remove it.

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