mtd: nand: atmel: Add ->setup_data_interface() hooks

The NAND controller IP can adapt the NAND controller timings dynamically.
Implement the ->setup_data_interface() hook to support this feature.

Note that it's not supported on at91rm9200 because this SoC has a
completely different SMC block, which is not supported yet.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>