input: atmel_mxt_ts: Support for secure touch polling

Add support for polling to the secure touch sysfs notification
file.
Stop the secure touch on reception of the FB_EARLY_EVENT_BLANK
event from the framebuffer driver.

Change-Id: I08603c7ba9fdf041460f285bfc61d93541c79752
Acked-by: Christian Bolis <cbolis@qti.qualcomm.com>
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>