ARM: shmobile: remove unnecessary platform_device as header cleanup

8e0e7aae
(ARM: shmobile: Drop r8a7779_add_device_to_domain())
removed last user of struct platform_device on this header.
It is no longer needed

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>