bmpblk: add nautilus board

Add nautilus to the list of boards.

BUG=b:66458931
BRANCH=None
TEST=emerge-nautilus chromeos-bmpblk
Signed-off-by: Chris Wang <chriswang@ami.corp-partner.google.com>

Change-Id: Ib639f68b6acf1fa12096ffd98b389508fe6af080
Reviewed-on: https://chromium-review.googlesource.com/702181
Commit-Ready: Chris Wang <chriswang@ami.corp-partner.google.com>
Tested-by: Chris Wang <chriswang@ami.corp-partner.google.com>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>