sh-pfc: Move private definitions and declarations to private header

Move all private structure definitions and function declarations from
include/linux/sh_pfc.h to drivers/sh/pfc/core.h.

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