input: it7258_ts_i2c: add DT support

Add DeviceTree support for ITE Tech. touch controller driver.
The data is represented in device tree format and parsed
by the driver using of framework APIs.

This is propagation gerrit for 8909w bring up.

Change-Id: I2671b7c30b0f2ed1d7ad788f29b7f900a2a1cdcc
Signed-off-by: Himanshu Aggarwal <haggarwa@codeaurora.org>
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>