mtd: nand: Update driver to match new DT binding

New binding changed node name from flash@e1000000 to nand-controller@0,0
which should be reflected in the driver. Both names are supported for
backward compatibility.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/61f6edd965e0c0b179184823d5283c6c61a1eb35.1645625433.git.michal.simek@xilinx.com