ARM: dts: imx51: Fix USB PHY duplicate unit-address

Currently the following DTC warnings are seen with W=1:

arch/arm/boot/dts/imx51-babbage.dtb: Warning (unique_unit_address): /usbphy/usbphy@0: duplicate unit-address (also used in node /usbphy/usbh1phy@0)
arch/arm/boot/dts/imx51-eukrea-mbimxsd51-baseboard.dtb: Warning (unique_unit_address): /usbphy/usbphy@0: duplicate unit-address (also used in node /usbphy/usbh1phy@0)

Fix it by moving the USB PHY nodes outside of simple-bus and drop the
unneeded unit-address, which matches the bindings documentation
at Documentation/devicetree/bindings/usb/usb-nop-xceiv.txt

While at it rename the USB PHY node to usbphy1 for consistency.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>