ARM: dts: at91: Switch to the new NAND bindings

Use the new EBI/NAND bindings to declare NAND chips and remove old NAND
nodes along the way.

Note that we keep using old bindings in at91rm9200.dtsi because this
SoC is not supported by the EBI driver.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>