Audio V4: Rename audio/device to audio/core

The name device has already too many meaning, thus rename the main audio
api to core.

Bug: 38184704
Test: compile
Change-Id: I178dfef05af8f8579196affbe2cbc5f6c3f9af55
Signed-off-by: Kevin Rocard <krocard@google.com>
diff --git a/audio/common/README b/audio/common/README
index 88cea46..cd03106 100644
--- a/audio/common/README
+++ b/audio/common/README
@@ -1 +1 @@
-This folder contains code common to audio device and effect API
+This folder contains code common to audio core and effect API