USB: xhci-plat: fix legacy PHY double init

Commits 7b8ef22e ("usb: xhci: plat: Add USB phy support") and
9134c1fd ("usb: xhci: plat: Add USB 3.0 phy support") added support
for looking up legacy PHYs from the sysdev devicetree node and
initialising them.

This broke drivers such as dwc3 which manages PHYs themself as the PHYs
would now be initialised twice, something which specifically can lead to
resources being left enabled during suspend (e.g. with the
usb_phy_generic PHY driver).

As the dwc3 driver uses driver-name matching for the xhci platform
device, fix this by only looking up and initialising PHYs for devices
that have been matched using OF.

Note that checking that the platform device has a devicetree node would
currently be sufficient, but that could lead to subtle breakages in case
anyone ever tries to reuse an ancestor's node.

Fixes: 7b8ef22e ("usb: xhci: plat: Add USB phy support")
Fixes: 9134c1fd

 ("usb: xhci: plat: Add USB 3.0 phy support")
Cc: stable@vger.kernel.org      # 4.1
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Stanley Chang <stanley_chang@realtek.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Tested-by: Stanley Chang <stanley_chang@realtek.com>
Link: https://lore.kernel.org/r/20231103164323.14294-1-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>