ARM64: dts: marvell: Add pinctrl nodes for Armada 3700

Add the nodes for the two pin controller present in the Armada 37xx SoCs.

Initially the node was named gpio1 using the same name that for the
register range in the datasheet. However renaming it pinctr_nb (nb for
North Bridge) makes more sens.

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