Provide defaults for android.hardware.audio@6.0-impl

This will allow vendors to create instances of
this library with other names. A different name
is required if a vendor wants to provide a custom
version (e.g. in HIDL) of
android.hardware.audio@6.0-impl and still
be able to use the library itself (e.g. to load
audio.r_submix.default) -
android.hardware.audio.service does not load both
libraries and prefers the default one.

Bug: 161485545
Test: boot emulator, check if audio works
Signed-off-by: Roman Kiryanov <rkir@google.com>
Change-Id: I55c4f9b1386be3464ad0f5f2568423843e7eae88