Input: elantench - fix misreporting trackpoint coordinates

Some firmwares occasionally report bogus data from trackpoint, with X or Y
displacement being too large (outside of [-127, 127] range). Let's drop such
packets so that we do not generate jumps.

Signed-off-by: Phoenix Huang <phoenix@emc.com.tw>
Tested-by: Yufei Du <yufeidu@cs.unc.edu>
Link: https://lore.kernel.org/r/20210729010940.5752-1-phoenix@emc.com.tw


Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>