Staging: remove epl driver

This is no longer maintained upstream, and no one cares about it at all,
so delete it.

The fact that it is duplicating an existing network driver also is a
good reason to remove it, it's causing nothing but trouble right now.

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>