dt-bindings: net: ti: k3-am654-cpsw-nuss: Add J721e CPSW9G support

Update bindings for TI K3 J721e SoC which contains 9 ports (8 external
ports) CPSW9G module and add compatible for it.

Changes made:
    - Add new compatible ti,j721e-cpswxg-nuss for CPSW9G.
    - Extend pattern properties for new compatible.
    - Change maximum number of CPSW ports to 8 for new compatible.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>