input: synaptics_dsx_2.6: Propagating security fixes from msm-3.18

This commit is a squash of below security fixes from the
branch msm-3.18.

d95b239 input: synaptics_dsx_2.6: protect tmpbuf allocation
ac27665 input: touchscreen: fix buffer overflow issue in synaptics driver

Change-Id: Id81f89bb07a2b167edff5490882b8db8e96c7072
Signed-off-by: Venkata Prahlad Valluru <vvalluru@codeaurora.org>