misc: ds1682: Show device registers as unsigned

This patch leverages the fact that all DS1682 registers are unsigned to
merge two return paths into one. It also introduces val_le as used in
ds1682_store() to merge two endianness conversions into one.

Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>