pinctrl: sh-pfc: r8a7791: add EtherAVB pin groups

Add the EtherAVB pin groups to the R8A7791 PFC driver.

Also add the copyright for all the Cogent Embedded's past work on this file.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>