Enable DRM HIDL HAL by default

Eliminate ENABLE_TREBLE since it is obsolete.
Switching back to legacy DRM is still possible
by building with DISABLE_TREBLE_DRM=true

Change-Id: I6b921050dff6162112c60df21549fc93bc46e379
diff --git a/drm/libmediadrm/Android.mk b/drm/libmediadrm/Android.mk
index 14740e6..8e3cc40 100644
--- a/drm/libmediadrm/Android.mk
+++ b/drm/libmediadrm/Android.mk
@@ -13,7 +13,7 @@
     IDrmClient.cpp \
     IMediaDrmService.cpp \
     SharedLibrary.cpp
-ifeq ($(ENABLE_TREBLE), true)
+ifneq ($(DISABLE_TREBLE_DRM), true)
 LOCAL_SRC_FILES += \
     DrmHal.cpp \
     CryptoHal.cpp
@@ -31,7 +31,7 @@
     libmediautils \
     libstagefright_foundation \
     libutils
-ifeq ($(ENABLE_TREBLE), true)
+ifneq ($(DISABLE_TREBLE_DRM), true)
 LOCAL_SHARED_LIBRARIES += \
     android.hidl.base@1.0 \
     android.hardware.drm@1.0 \