ARM: berlin: add the LIBGPIO as a dependency for the BG2Q

The BG2Q has GPIOs driven by the dwapb GPIO driver. Add the LIBGPIO as a
dependency to be able to support them.

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