PHY model is being used on omap5 platforms even if port mode
is not OMAP_EHCI_PORT_MODE_PHY. So don't guess if PHY is required
or not based on PHY mode.

If PHY is provided in device tree, it must be required. So, if
devm_usb_get_phy_by_phandle() gives us an error code other
than -ENODEV (no PHY) then error out.

This fixes USB Ethernet on omap5-uevm if PHY happens to
probe after EHCI thus causing a -EPROBE_DEFER.

Cc: Johan Hovold <johan@kernel.org>
Cc: Ladislav Michl <ladis@linux-mips.org>
Reported-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>