staging: comedi: cb_pcidas: simplify the boardinfo

The boardinfo values 'has_ai_trig_gated' and 'has_ai_trig_invert'
are both only set for the "1602" versions of the boards supported
by this driver.

Simplify the boardinfo, and the code, by replacing these two
variables with one "is_1602" variable.

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