input: touchscreen: Add force fw_update support via sysfs entry

Add sysfs entry for force fw_update support in Goodix
driver.
Change the usage of kstrtoul to sscanf in driver to avoid
portability issues.

This patch is propagated from msm-3.10.
(commit: 08cd82422df5c1c0473bfe00458869aaeb7aa072
input: touchscreen: Add force fw_update support via sysfs entry)
Also cleared checkpatch warnings on msm-3.18 kernel.

CRs-fixed: 579806
Change-Id: I147a3e465170dda7af415ade29c04257d9b11a6b
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>