staging: comedi: ni_65xx: hook up command support only if irq is available

Subdevice 3 is used in this driver to provide edge detection of the input
channels.

Move the reset/disable of the interrupts and the request_irq() so that
when subdevice 3 is setup we can conditionally hookup the async command
support only if the irq is available.

Also, remove the noise when the irq is not available.

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>