linux-phytec-ti

usb: otg: Move phy interface to separate file.

As otg.h is containing lots of phy interface related
stuff, moving all phy interface related stuff to new
file named phy.h

Signed-off-by: Venu Byravarasu <vbyravarasu@nvidia.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>