ARM: shmobile: marzen-reference: Move clock and OF device initialisation into board code

Move the clock initialisation and OF device population from
SoC to board code. This is in keeping with the pattern used by Lager.
And the clock portion is part of decoupling clock initialisation
from SoC code in preparation for moving to the common clock framework.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>