synaptics_3k: Improve touchscreen sensitivity

Increasing sensitivity in this manner has worked well on for the d2
touchscreen
driver. Apply to k2u/k2_ul.

0xlab did similar for DevKit8000 here:

https://gitorious.org/0xlab-kernel/kernel/commit/f5a258642408fd7820d7aefc58d1eb3719e06b8a

idea is taken here -
https://github.com/poondog/joey-m7-GPE/commit/06d3edc93fee81adf8ec1cafb2ae5204090821c1