ARM: dts: berlin: relicense the berlin2 dtsi under GPLv2/X11

The current GPLv2 only licensing on this dtsi makes it very impractical
for other software components licensed under another license.

In order to make it easier for them to reuse our device trees, relicense
this dtsi under a GPLv2/X11 dual-license.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>