staging: comedi: 8255: remove have_irg and refactor subdev_8255_init_irq

The have_irq variable in the 8255 private data is not used by the driver,
remove it.  This removes the need to access the private data in the
subdev_8255_init_irq function.

Also, add a bit of whitespace to improve the readability.

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