install drm libraries and drmserver to the core product, which covers sdk build

o related-to-bug: 6246463

Change-Id: Ifaef3cd71d05c7e1ca3d7b3c459bfa4bea0d2e20
diff --git a/target/product/core.mk b/target/product/core.mk
index 38a5a6c..318ed38 100644
--- a/target/product/core.mk
+++ b/target/product/core.mk
@@ -56,6 +56,7 @@
     dexlist \
     dexopt \
     dmtracedump \
+    drmserver \
     dx \
     ext \
     framework-res \
@@ -75,6 +76,8 @@
     libaudioutils \
     libcrypto \
     libdvm \
+    libdrmframework \
+    libdrmframework_jni \
     libexpat \
     libfilterfw \
     libfilterpack_imageproc \