arm64: dts: ls1028a: disable usb controller by default

One of the last devices which are enabled by default are the USB
controllers. Although the pins are not multi-function pins, some boards
might not use USB at all. Apply the "disabled-by-default" style also for
the USB controllers and enable the controllers in the actual device tree
of the boards.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>