Convert libmedialogservice to Android.bp

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

Removes AUDIOSERVER_MULTILIB which doesn't effectively do much for this
code -- we'll only build and install the versions necessary to support
the libraries/binaries depending on this library.

Test: mmma frameworks/av/services/medialog
Change-Id: Id47b1de95d3c62f0d2dbef69b26fefd6128e7f7e