package/uboot-tools: fix legal-info
Add hash for LICENSE file
Fixes:
$: make uboot-tools-legal-info
>>> uboot-tools 2019.04 Collecting legal info
ERROR: No hash found for Licenses/gpl-2.0.txt
Signed-off-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>