Added an API devm_usb_get_phy_by_phandle(), to get usb phy by passing a
device node phandle value. This function will return a pointer to
the phy on success, -EPROBE_DEFER if there is a device_node for the phandle,
but the phy has not been added, or a ERR_PTR() otherwise.

Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: NKishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>