Instead of writing to "nand->reg + REG_FMICSR" we write to "REG_FMICSR"
which is NULL and not a valid register.
Fixes: 8bff82cbc308 ('mtd: add nand support for w90p910 (v2)') Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Brian Norris <computersforpeace@gmail.com>