HID: wacom: Fix sensor outbounds and redefine as offsets from each edge

Many of Wacom's display tablets include an "outbound" area where pen
digitizing is possible but outside of the display area. To ensure that
pen coordinates are mapped to the correct on-screen location, the driver
sets the minimum and maximum axis values of X and Y to those coordinates
which coincide with the screen edge. These values are simply the
hardware minimum/maximum plus/minus the outbound size for a particular
edge.

When outbound support was added/updated in ac414da3, fa770340, and
ecd618dc, we decided to have the wacom_features structs store the desired
minimum and maximum values directly. In hindsight, this was perhaps not
the best choice since it has allowed minor errors to crop up unnoticed.
Some tablets have had their coordinates over-corrected (e.g. most of the
devices "fixed" in ecd618dc were already adjusted in ac414da3), while
others never had a correction applied (e.g. the ISDv5 325, whose
declared maximum the hardware maximum instead of the outbound maximum).

A less error-prone method of handling the outbound is to let the driver
calculate the correct minimum/maximum values by providing it with both
the actual hardware maximums and the size of the outbound on each edge.
These values are more easy to verify as correct since the values can be
trivially compared against specifications.

This patch reverts the declared maximum values to the actual hardware
maximums, e.g. as declared prior to ac414da3

 (values for these and other
display tablets that were subsuquently introduced have been verified
against specs). Per-edge outbound sizes are stored in the wacom_features
struct as offset_{left,right,top,bottom} and used in combination with
the hardware ranges to calculate effective axis ranges for ABS_X and
ABS_Y.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>