pinctrl: sh-pfc: r8a7795: add EtherAVB support

This patch adds EthernetAVB

Based on a much lager patch by Takeshi Kihara which was
originally posted by Kuninori Morimoto.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
[horms: extracted from a larger patch;
        corrected swapped {MATCH,CAPTURE_A} pins]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>