drm_hwcomposer: Fix build warnings

A cleanup patch to fix the build warnings that have surfaced
from the new build system.

BUG=None
TEST=Builds without warnings

Change-Id: I2ad898e627d451f87705d2bdf06a315b8e1c7a1c
Signed-off-by: Sean Paul <seanpaul@chromium.org>
3 files changed