ARM: shmobile: r8a7790: Constify platform data and resources

Platform data and resources for core devices are kmemdup()ed when the
corresponding devices are registered and can thus be declared as const.
Do so.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>