Move USB PHY bindings under usb directory to phy directory which already
contains other USB PHY bindings.

The Samsung USB PHY binding is obsolete and can be removed.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>

Driver handles PHY initialization, clock management, power
management and workarounds required after resetting the hardware.
Signed-off-by: Ivan T. Ivanov <ivan.ivanov@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>