Add a scale output parameter in process_scan_1 so that we pass scale
information from each driver read to the driver, and apply the scale
before passing it on to the main daemon.
Closes#28
In most IIO sensor types, _scale and _offset is added to the scan element base
name, for example:
in_accel has in_accel_scale and in_accel_offset
For compasses, this is different. Instead of being named
in_rot_from_north_magnetic_tilt_scale aand similar, the _scale and_offset
attributes are named in_rot_scale and in_rot_offset.
This commit adds a workaround to special-case the attribute naming for this
type of sensor.
