sh-pfc: Remove configuration dry-run and free

The purpose of the dry-run is to ensure that a pin about to be
configured isn't in use. However, the current implementation is a no-op.
This proves that the dry-run isn't essential. Remove it.

Freeing configuration then becomes a no-op as well. Remove it.

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