Input: elan_i2c - use iap_version to get firmware information

When driver is in IAP mode ic_type query may return 0xff. However
iap_version will always be valid, so let's use it to determine parameters
of the firmware that the controller is supposed to accept.

Signed-off-by: Duson Lin <dusonlin@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>