dt-bindings: mfd: ti,j721e-system-controller: Add SoC chip ID

The system-controller node also contains the chip-id node that is used
to identify the SoC specific properties. Add a pattern property to
match to the same, and add to the example.

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230418010019.1222431-1-nm@ti.com