binder: Expose an aidl interface module

Restructure the binder related makefile sections to expose a separate
|libwpa_binder_interface| which can be imported by clients/tests.

While there,
Change the name of the binder service to the name used in the selinux
permissions.

BUG: 29879355
Change-Id: I4a337964ca5be040e56698659c8d49679ab12105
TEST: Compiles
Signed-off-by: Roshan Pius <rpius@google.com>
3 files changed