mtd: rawnand: arasan: Fix a macro parameter

This macro is not yet being used so the compilers never complained
about it.

Fix the macro before using it.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-21-miquel.raynal@bootlin.com