nand/denali: use iowrite32() to replace denali_write32()

denali_write32() just implements a debug function for iowrite32(),
only print out the write value. Remove this function since it's useless

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>