Staging: add epl stack

This is the openPOWERLINK network stack from systec electronic.

It's a bit messed up as there is a driver mixed into the
middle of it, lots of work needs to be done to unwind the
different portions to make it sane.

Cc: Daniel Krueger <daniel.krueger@systec-electronic.com>
Cc: Ronald Sieber <Ronald.Sieber@systec-electronic.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>