hwc: Rename libexternal to serve HDMI as primary or external

This change will make is easier to build new functionality
applicable to both HDMI scenarios.

Change-Id: I417184568cb65a49c2ccb4199aff313ae2ee9b24
diff --git a/libhwcomposer/Android.mk b/libhwcomposer/Android.mk
index 8e3fc8e..df3e464 100644
--- a/libhwcomposer/Android.mk
+++ b/libhwcomposer/Android.mk
@@ -9,7 +9,7 @@
                                  $(TOP)/external/skia/include/core \
                                  $(TOP)/external/skia/include/images
 LOCAL_SHARED_LIBRARIES        := $(common_libs) libEGL liboverlay \
-                                 libexternal libqdutils libhardware_legacy \
+                                 libhdmi libqdutils libhardware_legacy \
                                  libdl libmemalloc libqservice libsync \
                                  libbinder libmedia