[PARISC] [MUX] Get the hversion directly from the parisc_device

Willy pointed out the hversion is already stored
in the parisc_device, so I do not need to extract
this information directly from the IODC data.
Also by using the information in the parisc_device
I can avoid re-reading the IODC data for the Muxes
with specifed port counts.

Signed-off-by: Ryan Bradetich <rbrad@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>