The CPSW9G instance of CPSW Ethernet Switch on TI's J784S4 SoC supports
additional PHY modes like QSGMII. Add a compatible for it.

Enable the use of "ti,qsgmii-main-ports" property for J784S4 CPSW9G.
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230315092408.1722114-1-s-vadapalli@ti.comSigned-off-by: Vinod Koul <vkoul@kernel.org>