input: touchscreen: Add Touch screen driver for IC it7258

This is the reference driver source code of it7258 touchscreen driver.
Signed-off-by: Alfred Deng <Alfred.Deng@ite.com.tw>
Git-commit: 3852a7ccce89c17ec3c4165acf9c81753c940104
Git-repo: git://github.com/ite-touch/touchscreen-driver



This is propagation gerrit for 8909w bring up.

Change-Id: Ic1eab3ba79b8e8e5c259bb92f2692fd0db5fc8d3
Signed-off-by: Himanshu Aggarwal <haggarwa@codeaurora.org>
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>