celox: Create a separate board file for storage devices

 - modeled after 0c547bbe082fb5f98189ccc79ea7581d9b5c3063

Change-Id: I8d498ec678b80355c117192d6ebfa964fb938a50
celox: move declarations to a header

Change-Id: Id25d744c996e015aecf217c1a0f19629681211cf