input: touchscreen: add palm-gesture sleep feature

Add palm-gesture sleep feature for ITE tech touchscreen
driver. When enabled the driver sends a key code to the
user space. Two optional device-tree properties are added
for this: ite,palm-detect and ite,palm-detect-keycode.

Change-Id: I0989cb66ab5edb10769ced9d525bd4f6d7adb02b
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>