openvmtools: fix legal info

In ab71dff0 it was moved to SUBDIR, but this was never reflected for the
legal-info files, update this to fix:
http://autobuild.buildroot.net/results/836/8363943cc9c967713f585209408ea087a052a12d/



[Thomas: put OPENVMTOOLS_SUBDIR before OPENVMTOOLS_LICENSE_FILES, as
suggested by Yann.]

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Karoly Kasza <kaszak@gmail.com>
Tested-by: Karoly Kasza <kaszak@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>