dt-bindings: iommu: renesas,ipmmu-vmsa: Add r8a774e1 support

Document RZ/G2H (R8A774E1) SoC bindings.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/1594676120-5862-2-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Rob Herring <robh@kernel.org>