mesh: Clarify API for empty model arrays
mesh: Clarify API for empty model arrays

Avoid applications defining empty model arrays by themselves by
documenting the BT_MESH_MODEL_NONE helper macro (renamed to be more
intuitive).

X-Original-Commit: 828eb55f39ca661165c58a736a649ca275616e0d

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble