dmamatch never added in the offset for the dma registers to the VA,

dmamatch never added in the offset for the dma registers to the VA,
and thus probed the wrong address on the 4/300 (but it worked because
it was probing the esp0 registers!).

now that bus_tmp() adds the offset in for us [as of obio 1.15] i
discoved that a byte access to the dma registers is not allowed.
so, i've change probeget to use a word access.