ARM: dts: mvebu: 98dx3236: Rename nand controller node

Update the 98dx3236 SoC and dependent boards to use
"nand-controller" instead of "nand".

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