package/opencv3: add license hash

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/opencv3/opencv3.hash

@@ -1,2 +1,4 @@
 # Locally calculated
 sha256 8bb312b9d9fd17336dc1f8b3ac82f021ca50e2034afc866098866176d985adc6  opencv3-3.3.0.tar.gz
+# License files, locally calculated
+sha256 e974db937899a2505f0eb43ece9d2f2eb36e8580ad88785e3ffac0d697ebaf5d  LICENSE