ARM: dts: armada-38x: Add NAND pinctrl information

Add pin control information for the NAND flash interface. This interface
is multiplexed with the device bus interface to the function is "dev"
not "nand" as one might expect.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>