phy: nop-phy: Add standard usb-nop-xceiv compat string

phy: nop-phy: Add standard usb-nop-xceiv compat string

The USB no-op PHY uses "usb-nop-xceiv" compatible string. This driver is
compatible with USB no-op PHY, so add the compatible string.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexey Brodkin <alexey.brodkin@synopsys.com>
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Jean-Jacques Hiblot <jjhiblot@ti.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Ye Li <ye.li@nxp.com>
Cc: uboot-imx <uboot-imx@nxp.com>