package/google-material-design-icons: add license hash

Partly fixes:
http://autobuild.buildroot.net/results/f0f/f0fd05ce8a8b595015baf625481b58967df53458/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/google-material-design-icons/google-material-design-icons.hash

@@ -1,2 +1,3 @@
 # Locally calculated
 sha256  769547061a51f81623bf5174767c08fc587fd6946339592fbd6cd0dd45f56b4c  2.2.3.tar.gz
+sha256  8ae9438818c26e4873b91d8c6ad620526c011e27e125677f13031eda903f007c  LICENSE