Now that the tswap() functions are available for target-independent
code, too, we can move xilinx_ethlite.c from specific_ss to softmmu_ss
to avoid that we have to compile this file multiple times.

Message-Id: <20230508120314.59274-1-thuth@redhat.com>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>