sdl2: update license file hash

Copyright year update.

Fixes:
http://autobuild.buildroot.net/results/2c8/2c865463a4b7524114518c04dce9c94252433460/

Cc: Guillaume Gardet <guillaume.gardet@oliseo.fr>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 5a8f887e7ab6c28b2d5a4c01266bc75943cea90c)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/sdl2/sdl2.hash

@@ -1,4 +1,4 @@
 # Locally calculated after checking http://www.libsdl.org/release/SDL2-2.0.8.tar.gz.sig
 sha256 edc77c57308661d576e843344d8638e025a7818bff73f8fbfab09c3c5fd092ec  SDL2-2.0.8.tar.gz
 # Locally calculated
-sha256 bbd2edb1789c33de29bb9f8d1dbe2774584a9ce8c4e3162944b7a3a447f5e85d  COPYING.txt
+sha256 61e627031e1160bf8b9bdbc9cda27656d422ea8eaab199b64b4a4a4168437154  COPYING.txt