uboot-tools: fix license issues

Fix license directory and filename change, fixes:
http://autobuild.buildroot.net/results/8c9/8c94c81fe74399c854de335329cf4942f8356fbe/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>