mainboard/google/poppy: Generate digitizer node in SSDT

Add support for generating digitizer node in SSDT using wacom i2c
driver.

BUG=None
BRANCH=None
TEST=Verified that the node shows up in SSDT.

Change-Id: If7e1e2463778c2ff7263eff995def149457edcde
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/18373
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2 files changed