get Synatics touchpad

  The previous method for getting Synaptics device information through open source dirver does not work in current build, which now adopts Synaptics closed source driver.

  In current method, I need to turn off Synaptics raw mode so that I can probe /sys/class/input to get Synaptics device informatioin.

Change-Id: I0d4589db7f50f289516ceee1cc6a5e0503589922

BUG=
TEST=

Review URL: https://chromereview.prom.corp.google.com/1641037
1 file changed