pinctrl: sh-pfc: Support named pins with custom configuration

Pins not associated with a GPIO port can still have other configuration
parameters. Add a new macro SH_PFC_PIN_NAMED_CFG which allows for named
pins to be declared with a set of configurations. The new macro is an
modification of SH_PFC_PIN_NAMED to allow for optional configuration to
be assigned.

The flag SH_PFC_PIN_CFG_NO_GPIO is still enforced as this should only be
used to define pins not associated with a GPIO port.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>