phy: ti: phy-gmii-sel: Add support for CPSW9G GMII SEL in J784s4

Each of the CPSW9G ports in J784s4 supports modes such as QSGMII.

Add a new compatible for it and extend the qsgmii-main-ports support
for J784s4.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>