Document VSPD found in RZ/G2L SoC. VSPD block is similar to VSP2-D
found on R-Car SoC's, but it does not have a version register and
it has 3 clocks compared to 1 clock on vsp1 and vsp2.

This patch introduces a new compatible 'renesas,r9a07g044-vsp2' to
handle these differences.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>