The trackpad bits in the DTS needed some love.  This adds some basic
infrastructure support in the main gru dts file and then adds the
specific trackpad used on kevin-r0 and kevin-r1.  For now just duplicate
between kevin-r0 and kevin-r1 and we'll decide if we want to share
later (perhaps we want an "atmel" snippet?).

Note that gpio-keymap here makes the driver appear as a trackpad rather
than a touchscreen (driver assumes that anything with buttons is a
trackpad).  Input entry corresponding to the button on the trackpad was
found by experimentation as suggested in the device tree bindings.

BUG=chrome-os-partner:52637
TEST=With series, trackpad works in browser; button works.

Change-Id: Ia62cff90449625778fd99054b914e22a55c13550
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-on: https://chrome-internal-review.googlesource.com/256510


Commit-Ready: Doug Anderson <dianders@google.com>
Tested-by: Doug Anderson <dianders@google.com>
Revi...