gn-build: Get HCI and net_test_hci to compile

This CL fixes the HCI module so that the HCI static library and the net_test_hci
unit test can be compiled using GN + ninja.

BUG=21339022,21444689

Change-Id: If3d8649b25297880e5e674a2026badb1b0e01fee
5 files changed