Input: elants_i2c - support palm detection

Input: elants_i2c - support palm detection

Elan uses the least significant bit of byte 33 to signal the type of
contact (finger versus palm). The default value is 1 for all firmwares,
which is reported as MT_TOOL_FINGER. If firmware supports palm detection,
the bit will change to 0 and the driver will report such contact as
MT_TOOL_PALM.

Signed-off-by: Johnny Chuang <johnny.chuang@emc.com.tw>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Link: https://lore.kernel.org/r/1585551756-29066-1-git-send-email-johnny.chuang.emc@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>