staging: ion: Add files for parsing the devicetree

Devicetree is the preferred mechanism for platform definition
these days. Add a set of files for supporting Ion with devicetree.
This includes a set of bindings for heaps common across all
devices and parsing methods. Clients may use the standard
bindings or they can call the parsing functions along with
their own parsing for platform specific heaps.

Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>