pinctrl: sh-pfc: r8a7795: Add EtherAVB pins, groups and function

Add pins, groups, and a function for EtherAVB on R-Car H3 ES2.0.

Extracted from a big patch in the BSP by Takeshi Kihara.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>