Input: iqs5xx - allow more time for ATI to complete

Input: iqs5xx - allow more time for ATI to complete

After the device is initialized, it runs ATI (calibration) during
which it cannot readily respond to I2C communication. To keep the
open and close callbacks from writing to the device too soon, the
driver waits 100 ms before returning from probe.

The vendor reports that ATI may actually take up to 250 ms to run
(including margin), so increase the delay accordingly. Update the
comments to clarify the reason for the delay as well.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/1611002626-5889-9-git-send-email-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>