udev-extraconf: change LICENSE to MIT

udev-extraconf: change LICENSE to MIT

* Original recipe added by RP in fc128ab1e4fec27d44cebfa690a9bc233eda0caf
  was saying GPL (later GPLv2)
* COPYING.GPL was added to reflect that
* Meta-oe has similar recipe with MIT license and even more scripts, so lets
  change LICENSE here too
* Most code was derived from the meta-oe version or added to OE arguably
  under MIT and the MIT license makes most sense here

(From OE-Core rev: 54a4a0b42d4515260841229d69f9cc43485bcb78)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>