ARM: dts: berlin2q: Add missing unit name to /soc node

This patch fixes the following DTC warning with W=1:

"Node /soc has a reg or ranges property, but no unit name"

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>