ARM: shmobile: sh73a0: Register PFC platform device

Add arch code to register the PFC platform device instead of calling the
driver directly. Platform device registration in the sh-pfc driver will
be removed.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>