Input: elan_i2c - make fetching IC type of older controllers more robust

On older controllers IC type is reported in the 2nd byte of
ETP_I2C_OSM_VERSION_CMD, however if controller's firmware is not flashed
correctly it may return incorrect data. Fortunately there is also
ETP_I2C_IAP_VERSION_P0_CMD command that can be used when controller in
either normal or IAP mode, and which is guaranteed to return accurate data,
so let's use it.

Signed-off-by: Jingle Wu <jingle.wu@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>