package/firmware-imx: fix legal-info

Part of fimrware-imx were dropped in the new version, so we have less
legal-info to save.

Fixes:
    http://autobuild.buildroot.org/results/59b/59b09152700a5839af46edb554e53981569f8921



Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>