Input: melfas_mip4 - report palm touches

The driver had the code to differentiate between finger and palm touches,
but did not use this information when reporting contacts. Change it so that
proper "tool" type is assigned to reported contacts.

Signed-off-by: JungHoon Hyun <hyunjunghoon@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>