->setup_data_interface() is a controller specific method and should
thus be placed in nand_controller_ops.

In order to make that work with controllers that support keeping
pre-configured timings we need to add a new NAND_KEEP_TIMINGS flag to
inform the core it should skip the timings selection step.
Signed-off-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Tested-by: NJanusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>