Remove hal_impl_domain deprecation warning

This removes the compile-time deprecation warning about
hal_impl_domain macro. The warning was introduced in
86e87806f5777a7fc09ea962e694442297e4f8d6. We don't want to spam all
Android platform developers about something internal to the ongoing
SELinux policy restructuring.

Test: Policy compiles without any warnings
Test: Google Play Movies plays back movies (i.e., DRM HAL works)
Bug: 34170079
Change-Id: Icbd4d1283196f7ccc84c2a041c5601113d3c9f21