pinctrl: renesas: r8a77980: Add bias pinconf support

Implement support for pull-up and pull-down handling for the R-Car V3H
SoC, using the common R-Car bias handling.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/448f47ccd89d9bc8621c7fda8c81508deb05cb82.1619785375.git.geert+renesas@glider.be