usb: usb251xb: Reallow swap-dx-lanes to apply to the upstream port

usb: usb251xb: Reallow swap-dx-lanes to apply to the upstream port

This is a partial revert of 73d31def1aab "usb: usb251xb: Create a ports
field collector method", which broke a existing devicetree
(arch/arm64/boot/dts/freescale/imx8mq.dtsi).

There is no reason why the swap-dx-lanes property should not apply to
the upstream port. The reason given in the breaking commit was that it's
inconsitent with respect to other port properties, but in fact it is not.
All other properties which only apply to the downstream ports explicitly
reject port 0, so there is pretty strong precedence that the driver
referred to the upstream port as port 0. So there is no inconsistency in
this property at all, other than the swapping being also applicable to
the upstream port.

CC: stable@vger.kernel.org #5.2
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://lore.kernel.org/r/20190719084407.28041-3-l.stach@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>