input: touchscreen: correct function and variable names in ITE tech driver

Correct function and variable names in ITE tech driver from upper case
to lower case, and use underscore instead of camel-case in their names.
This change makes the driver as per kernel coding standards and similar
to other touch drivers.

CRs-Fixed: 982219
Change-Id: Ic8b66317f414fe3bfcd0f9c5b03369cc304edb55
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>