MSM: add trackpad driver in st1.5

BUG=NONE
TEST=Built and ran on st1.5

Review URL: http://codereview.chromium.org/724001



Signed-off-by: Horace Fu <horace.fu@quantatw.com>
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>
Change-Id: I354c0c1ccba76f2af7c0fae7d9acec3501039138