pinctrl: renesas: r8a77970: Add bias pinconf support

Implement support for pull-up (most pins, excl. DU_DOTCLKIN and EXTALR)
and pull-down (most pins, excl. JTAG) handling for the R-Car V3M 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/bcfad447624d874258a45a92554574b8fe9f712f.1619785375.git.geert+renesas@glider.be