pinctrl: renesas: r8a77470: Add bias pinconf support

pinctrl: renesas: r8a77470: Add bias pinconf support

Implement support for pull-up (most pins) and pull-down (ASEBRK#/ACK)
handling for the RZ/G1C SoC, using the common R-Car bias handling.

Note that on RZ/G1C, the "ASEBRK#/ACK" pin is called "ACK", but the code
doesn't handle that naming difference.  Hence users should use the R-Car
naming in DTS files.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/18c8ebf9fa9e239253a723857e9dffeec775db7e.1619785375.git.geert+renesas@glider.be