HID: wacom: generic: Add support for vendor-defined "Sense" usage

Wacom's professional tablets beginning with the Intuos4 are capable of
reporting an intermediate degree of proximity where the pen is no longer
close enough to communicate with ("in prox"), but still close enough to
be sensed ("in range"). This additional state is particularly useful for
performing palm rejection as it allows the driver to disable the touch
sensor while the pen is a greater distance from the tablet.

Like other professional tablets, the new MobileStudio Pro also reports
this intermeidate "in range" proximity state. Its descriptor assigns
usage 0xff0d0036 to this bit. Normally 'wacom_equivalent_usage' would
translate this to the standard HID "Quality" usage, but since this has
a different meaning we have it explicitly ignore the usage and define
it ourselves as "Sense" (since "In Range" is already defined by the
HID standard and interpreted by our driver as meaning "in prox").

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>