Fix previous commit (r253873).  "cong" has one bit per channel but the
congestion channel map has 1 nibble per channel.  So bits wxyz need to
be blown up into 000w000x000y000z.
Display temperature sensor data.  Shows -1 if sensor not
available on the card.

# sysctl dev.t4nex.0.temperature
# sysctl dev.t5nex.0.temperature