pinctrl: sh-pfc: r8a77990: Add bias pinconf support

This patch implements control of pull-up and pull-down. On this SoC there
is no simple mapping of GP pins to bias register bits, so we need a table.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>