Add support for the more rare volume usage which differs compared to the

Add support for the more rare volume usage which differs compared to the
more common volume increment/decrement usages in which each volume
change direction is represented using a distinct usage. The volume usage
instead uses bits of the interrupt buffer to represent the wanted
volume. The same bits should be within the bounds given by the logical
min/max associated with the HID item. However, the volume is not
interpreted as an absolute value but rather just looking at the sign bit
in order to determine the volume change direction.

I couldn't find any documentation of this usage and the implementation is
therefore solely based on analysing actual data from Richard Toohey's
<richardjtoohey at gmail dot com> Dell keyboard.