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 if a palm is detected. Two optional device-tree
properties are added for this: ite,palm-detect and
ite,palm-detect-keycode.

This is propagation gerrit for 8909w bring up.

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