mtd: nand: denali: remove unnecessary writes to ECC_CORRECTION

Because SUPPORT_15BITECC is defined, the following is dead code:

  #elif SUPPORT_8BITECC
          iowrite32(8, denali->flash_reg + ECC_CORRECTION);
  #endif

Such ifdefs are useless and unacceptable coding style.

These writes are not needed in the first place since ECC_CORRECTION
is set up by the nand_init() function.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>