mb/google/poppy/variants/nautilus: enable digitizer pen device

- Add pen device property into devicetree.cb.
- Set GPP_C9 to 0 as default.

BUG=none
BRANCH=master
TEST=emerge-nautilus coreboot and check pen device operation
Signed-off-by: Seunghwan Kim <sh_.kim@samsung.com>
Change-Id: I050671c8b46fd92b1dd9164be2646727cd67da9f
Reviewed-on: https://review.coreboot.org/23010
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
2 files changed