audiopolicy: engineconfigurable: Don't include the example

When using the configurable policy engine, the audiopolicy makefile
implicitly declares dependencies on the configuration files. However,
the example folder already contains the example files which we wan't to
override.

This patch removes the example from the makefile inclusion path so that
we can declare it on a per-device basis without getting errored out by
duplicate module names.

Change-Id: Ie47ebff6b13606c93630c017252ebaa204203a76