sh: Remove unused sh_pfc_register_info() function

All boards use sh_pfc_register() directly, remove the unused
sh_pfc_register_info() function.

Make the name argument to sh_pfc_register() mandatory as it's now
supplied by all callers.

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>