libbinder: add build option for single-threaded RPC

Trusty does not support threading. This adds a build option
to disable mutexes and other threading code from RpcState,
RpcSession, and RpcServer.

Bug: 224644083
Test: build Trusty
Change-Id: Iaa78caca1ddee45be7c2def2755598decc0d4d15
10 files changed