hw: Mark nd_table[] misuse in realize methods FIXME

nd_table[] contains NIC configuration for boards to pick up.  Device
code has no business looking there.  Several devices do it anyway.
Two of them already have a suitable FIXME comment: "allwinner-a10" and
"msf2-soc".  Copy it to the others: "allwinner-h3", "xlnx-versal",
"xlnx,zynqmp", "sparc32-ledma", "riscv.sifive.u.soc".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200715140440.3540942-3-armbru@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>