Add overlays for various serdes protocols on LS1028A QDS board using
different PHY cards.  These should be applied at boot, based on serdes
configuration.  If no overlay is applied, only the RGMII interface on
the QDS is available in Linux.

Building device tree fragments requires passing the "-@" argument to
dtc, which increases the base dtb size and might cause some platforms to
fail to store the new binary. To avoid that, it would be nice to only
pass "-@" for the platforms where fragments will be used, aka
LS1028A-QDS. One approach suggested by Rob Herring is used here:

https://lore.kernel.org/patchwork/patch/821645/

Also moved the enet* override nodes in dts file to be in alphabetic order.
Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Jason Liu <jason.hui.liu@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>