metag: of_platform_populate from arch generic code
If no init_machine callback is provided, call of_platform_populate()
instead. This allows a board/SoC that only needs to call
of_platform_populate to omit the callback altogether.
Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: Grant Likely <grant.likely@secretlab.ca> Cc: Rob Herring <rob.herring@calxeda.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: devicetree-discuss@lists.ozlabs.org