input: touchscreen: st: Disable PRESSURE event report

Android doesn't treat the touch event as a valid one when its
PRESSURE value which touch IC report is small. And its PRESSURE
is optional for this IC. So remove it.

Change-Id: Ib0ba97d1f834bf05a9a51f46e69be6e1aded531f
Signed-off-by: Xin Hua Lu <luxinhua@codeaurora.org>