sh-pfc: Add function to retrieve a pin instance from its pin number

This prepares support for sparse pin numbering. The function currently
just performs and indexed lookup in the pins array.

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