mtd: rawnand: fsmc: Make conversion from chip to fsmc consistent

nand_to_fsmc() is used almost everywhere except in
fsmc_setup_data_interface() where nand_get_controller_data() is used
instead. Make that consistent and drop the nand_set_controller_data()
call in the probe path.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>