HID: input: force generic axis to be mapped to their user space axis

Atmel 840B digitizer presents a stylus interface which reports twice
the X coordinate and then twice the Y coordinate. In its current
implementation, hid-input assign the first X to X, then the second to Y,
then the first Y to Z, then the second one to RX.

This is wrong, and X should always be mapped to X, no matter what.
A solution consists in forcing X, Y, Z, RX, RY, RZ to be mapped to their
correct user space counter part.

Reported-by: Éric Brunet <Eric.Brunet@lps.ens.fr>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>