systemd: do not recommend udev-extraconf for udev

systemd: do not recommend udev-extraconf for udev

* adding this extra functionality is an image- or distro-decision
* at least automount-rule/script breaks other automount solutions causing
  misleading kernel messages as 'VFS: could not find a valid V7 on sda'

same as already sent by Koen Kooi [1]

[1] http://patches.openembedded.org/patch/48139/

(From OE-Core rev: 860cd2f9ba5803824ab59bf9c0e84b83f7907dc1)

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>