ARM64: rockchip_cros_defconfig: Turn on atmel touchscreen driver

ARM64: rockchip_cros_defconfig: Turn on atmel touchscreen driver

The touchscreen driver is used for both atmel trackpads (AKA touchpads)
and touchscreens.  Turn it on so we can use it.

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

Change-Id: I316a8411c35ab7b48182cbe704c9f80114a5afcf
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-on: https://chrome-internal-review.googlesource.com/256511
Commit-Ready: Doug Anderson <dianders@google.com>
Tested-by: Doug Anderson <dianders@google.com>
Reviewed-by: Doug Anderson <dianders@google.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>