gtk+: Update LICENSE field version for 2.20.1 to LGPLv2
gtk+: Update LICENSE field version for 2.20.1 to LGPLv2

* Updated LICENSE field version from generic LGPL to LGPLv2,
  LGPLv2+, and LGPLv2.1 to reflect the real license version.
* This change was based on setting in oe-core as well as code
  inspection
* Verified for version 2.20.1 of gtk+

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

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