phy: ti: phy-j721e-wiz: add support for j7200-wiz-10g

j7200-wiz-10g supports 2 reference clocks. However, the
control bits for these clocks is in a separate register that
sits in the System Control register space. Handle that register.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>