PXA25xx SoCs don't have a USB controller, so drop the node from the
common pxa2xx.dtsi base file. Both pxa27x and pxa3xx have a dedicated
node already anyway.

While at it, unify the names for the nodes across all pxa platforms.
Signed-off-by: Daniel Mack <daniel@zonque.org>
Reported-by: Sergey Yanovich <ynvich@gmail.com>
Link: https://patchwork.kernel.org/patch/8375421/Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>