staging: comedi: quatech_daqp_cs: only hook up cmd support if we have an IRQ

Interrupts are only needed by this driver to support the analog input async
commands. Don't hook up the command support if pcmcia_request_irq() fails
instead of completely failing the (*auto_attach).

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>