Convert libsoundpool to Android.bp

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

Test: m -j checkbuild
Change-Id: If0b7cb1e2c86ff1be41c00d98fd9ddec31287a53
diff --git a/media/jni/Android.bp b/media/jni/Android.bp
index 41c5717..9686ab5 100644
--- a/media/jni/Android.bp
+++ b/media/jni/Android.bp
@@ -79,4 +79,5 @@
 
 subdirs = [
     "audioeffect",
+    "soundpool",
 ]