atk: Update LICENSE field version to GPLv2
atk: Update LICENSE field version to GPLv2

* Update LICENSE field version from generic LGPL to GPLv2+ and
  LGPLv2+ to reflect the real license version.
* This change was based on setting in oe-core as well as code
  inspection.

Signed-off-by: Chase Maupin <5a5662f468a76e0fc4391e65fb9f536df44d7380@ti.com>

mrchapp/arago-oe-dev,mrchapp/arago-oe-dev,sledz/oe,sledz/oe,sledz/oe,mrchapp/arago-oe-dev,mrchapp/arago-oe-dev,sledz/oe,mrchapp/arago-oe-dev,sledz/oe,sledz/oe,mrchapp/arago-oe-dev,mrchapp/arago-oe-dev,sledz/oe