staging: comedi: ni_labpc: fix command support with analog input subdevice

An interrupt is required for command support to work with the
analog input subdevice. When used with the ISA driver, enabling
the interrupt is optional. Fix the subdevice init so that command
support is only enabled if the irq is available.

Add some whitespace to the subdevice init. Change the 'maxdata'
value to hex as this is more common in comedi drivers.

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