phy: ti: am654: add support for USB super-speed

The SERDES PHY can support USB super-speed lane.
Add support for that.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Link: https://lore.kernel.org/r/20200513131254.10497-3-rogerq@ti.com
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>