arm: dts: ls1028a: disable the PCIe controller by default

Disable the PCIe controllers by default, just like in the linux device
tree. But there is one catch, for linux they are enabled in-place by the
bootloader. Obviously, this doesn't work for the bootloader. Thus we
explicitly enable the controllers in the -u-boot.dtsi files.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>