Input: atmel_mxt_ts - make wait-after-reset period compatible with all chips

The delay before the chip can be accessed after reset varies between
different chips in maXTouch family. Waiting for an interrupt and a T6
status message with the RESET bit set is a better behaviour.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Acked-by: Benson Leung <bleung@chromium.org>
Acked-by: Yufeng Shen <miletus@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>