net: ravb: Add R-Car Gen4 support

Add support for the Renesas Ethernet AVB (EtherAVB-IF) blocks on R-Car
Gen4 SoCs (e.g. R-Car V4H) by matching on a family-specific compatible
value.

These are treated the same as EtherAVB on R-Car Gen3.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/2ee968890feba777e627d781128b074b2c43cddb.1662718171.git.geert+renesas@glider.be


Signed-off-by: Jakub Kicinski <kuba@kernel.org>