drm_hwcomposer: remove unnecessary external includes

Linking to libraries will add necessary include paths, so we don't need to
list them explicitly.

Still need libsync for sw_sync.h until this dependency is removed.

Tested-by: Chih-Wei Huang <cwhuang@linux.org.tw>
Reviewed-by: Chih-Wei Huang <cwhuang@linux.org.tw>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/Android.mk b/Android.mk
index 109e352..8b11e37 100644
--- a/Android.mk
+++ b/Android.mk
@@ -48,11 +48,7 @@
 
 LOCAL_C_INCLUDES := \
 	external/drm_gralloc \
-	external/libdrm \
-	external/libdrm/include/drm \
-	system/core/include/utils \
-	system/core/libsync \
-	system/core/libsync/include \
+	system/core/libsync
 
 LOCAL_SRC_FILES := \
 	autolock.cpp \