dt-bindings: phy: ti: Add support for AM654x USB2 PHY

Add support for USB2 PHY on AM654x SoC.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>