phy: ti: gmii-sel: Enable SGMII mode for J7200

TI's J7200 SoC supports SGMII mode with the CPSW5G instance of the CPSW
Ethernet Switch. Thus, enable it by adding SGMII mode to the list of the
corresponding extra_modes member.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20230309063514.398705-3-s-vadapalli@ti.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>