arm64: dts: marvell: add gpio support for Armada 7K/8K

arm64: dts: marvell: add gpio support for Armada 7K/8K

Enable gpio support for CP and AP on the Marvell Armada 7K/8K SoCs.

The Armada 8K has two CP110 blocks, each having two GPIO controllers.
However, in each CP110 block, one of the GPIO controller cannot be
used: in the master CP110, only the second GPIO controller can be used,
while on the slave CP110, only the first GPIO controller can be used.

On the other side, the Armada 7K has only one CP110, but both its GPIO
controllers can be used.

For this reason, the GPIO controllers are marked as "disabled" in the
armada-cp110-master.dtsi and armada-cp110-slave.dtsi files, and only
enabled in the per-SoC dtsi files.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>