Differentiate between 622x, 625x, and 628x m-series boards. Fix adc reset

Differentiate between 622x, 625x, and 628x m-series boards.  Fix adc reset
for 625x boards, based on example code from ni (untested on hardware).
Fix polarity of AI_CONVERT output for 622x boards, based on ni
example code.  Do 32 bit pci transfers on analog output dma, now that
the sample ordering has been resolved through byte-swapping bits
in mite chip.  Use external clock (when configured) for timebase 3
too (I believe timebase 3 is the 80 MHz clock).