iommu/ipmmu-vmsa: Add r8a7796 DT binding

Update the IPMMU DT binding documentation to include the r8a7796 compat
string for R-Car M3-W.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Documentation/devicetree/bindings/iommu/renesas,ipmmu-vmsa.txt

@@ -16,6 +16,7 @@ Required Properties:
     - "renesas,ipmmu-r8a7793" for the R8A7793 (R-Car M2-N) IPMMU.
     - "renesas,ipmmu-r8a7794" for the R8A7794 (R-Car E2) IPMMU.
     - "renesas,ipmmu-r8a7795" for the R8A7795 (R-Car H3) IPMMU.
+    - "renesas,ipmmu-r8a7796" for the R8A7796 (R-Car M3-W) IPMMU.
     - "renesas,ipmmu-vmsa" for generic R-Car Gen2 VMSA-compatible IPMMU.
 
   - reg: Base address and size of the IPMMU registers.