[U-Boot] RFC: Migration target date for DM_ETH

[Heinrich Schuchardt]

Currently dozens of boards still do not use the driver model for the
network devices. This makes integration between devices in the UEFI
sub-system with the U-Boot devices complicated.

See: https://travis-ci.org/xypron2/u-boot/builds/569675547

In doc/driver-model/migration.rst I am missing a migration target day
for DM_ETH. Shouldn't define one? 2020-07 should be realistic.

Best regards

Heinrich