If we want systemd support we use systemd's udev, so disable systemd
support in this udev to avoid packaging the unit files.
(From OE-Core rev: 36aa37e693bcb76a96761847dbef6a015d96fd98)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>