sh-pfc: Configure pins as GPIOs at request time when handled externally

When a GPIO is handled by a separate driver the pinmux
gpio_set_direction() handler won't be called. The pin mux type then need
to be configured to GPIO at request time.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>