Convert libmediadrm to Android.bp

See build/soong/README.md for more information.

Test: m -j checkbuild
Change-Id: Icfc13bb5f55fa156ef72d3cf3a327e38739d775b
diff --git a/Android.bp b/Android.bp
index 7d46b2d..c4d6789 100644
--- a/Android.bp
+++ b/Android.bp
@@ -16,6 +16,7 @@
 
 subdirs = [
     "camera",
+    "drm/*",
     "media/*",
     "radio",
     "soundtrigger",