dm: net: Use existing Ethernet init for driver model

dm: net: Use existing Ethernet init for driver model

At present even with driver model is used there is still much manual init
of related devices: PHY, environment and board init. Until these requirements
are dealt with in another way we need to keep them around.

Break out the init portion of the legacy eth_initialize() into a separate
function and call it from both the legacy and driver model eth_initialize()
functions.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>