The main change is to send SDVO commands using data passed into the send
command function, and receive responses into memory passed into the read
response function, rather than stuff things in/out through dev_priv->sdvo_regs.
This lets us use structures to represent some arguments, which results in a
nice cleanup (and 100% fewer arguments named magicN as a side effect).
Also, the mode set path is changed to not do any preferred input timing
work. We weren't doing anything legitimate with the results, since we didn't
modify the CRTC timing appropriately, so now we just stuff the CRTC timing into
both and hope for the best. This should probably be revisited later.