input: synaptics_dsx: add checks of user input data

Add checks of the user input count to avoid possible heap overflow

Signed-off-by: Min Chong <mchong@google.com>
Bug: 30937462
Git-repo: https://android.googlesource.com/kernel/msm.git


Git-commit: a6accafb252a76256f11c83e28c556c8ca4b8e1f
Change-Id: I6fc8323cbcf395a2c24e49e65cc7012709d031a2
Signed-off-by: Dennis Cagle <d-cagle@codeaurora.org>