display: Add HDMI CEC HAL

Implement the spec as per
hardware/libhardware/include/hardware/hdmi_cec.h

Change-Id: I02e1ba9deee1007b7e5922c363b9f5d6c6ad82a9
diff --git a/Android.mk b/Android.mk
index a128327..5070911 100644
--- a/Android.mk
+++ b/Android.mk
@@ -5,6 +5,7 @@
 endif
 
 display-hals := libgralloc libcopybit liblight libmemtrack libqservice libqdutils
+display-hals += hdmi_cec
 
 ifeq ($(TARGET_USES_SDE), true)
     sde-libs := displayengine/libs