ARM: dts: am335x: Fix NAND device nodes

Add compatible id, GPMC register resource and interrupt
resource to NAND controller nodes.

The GPMC node will provide an interrupt controller for the
NAND IRQs.

Cc: Teresa Remmet <t.remmet@phytec.de>
Cc: Ilya Ledvich <ilya@compulab.co.il>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Rostislav Lisovy <lisovy@gmail.com>
Cc: Enric Balletbo i Serra <eballetbo@iseebcn.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>