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The Samsung USB PHY binding is obsolete and can be removed.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: NRob 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>

Added device tree support for TI's Keystone USB PHY driver and updated the
Documentation with device tree binding information.
Signed-off-by: NWingMan Kwok <w-kwok2@ti.com>
Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>