staging: comedi: das08: abbreviate IS_ENABLED()

The `IS_ENABLED(CONFIG_COMEDI_DAS08_ISA)` and
`IS_ENABLED(CONFIG_COMEDI_DAS08_PCI)` macro calls are a bit long-winded.
Define a couple of macros `DO_ISA` and `DO_PCI` as abbreviations for
them.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>