Input: elants_i2c - disable idle mode before updating firmware

If the device is in idle mode and is in the middle of a scan it may not
have a chance to react to the reset and then IAP commands within required
time interval and firmware update may fail. Let's bring the device out of
idle mode before attempting to reset it so that the scan period is smaller
and thus it can react to the command quicker.

Signed-off-by: James Chen <james.chen@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>