pinctrl: sh-pfc: r8a77990: Add EthernetAVB pins, groups and functions

This patch adds group and function of AVB PHY, LINK, MAGIC, MII and PTP
pins for the R8A77990 SoC.

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>