pinctrl: sh-pfc: r8a7778: Add bias (pull-up) pinconf support

On this SoC there is no simple mapping of GP pins to pull-up register
bits, so we need a table.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>