ryu: add support for p4 boards

BUG=none
BRANCH=none
TEST=P4 board boots and selects correct dts file

Change-Id: If14e2586c4ef5b44af1754b3f06126b79473798b
Signed-off-by: David Riley <davidriley@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/250634
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
2 files changed