mtd: nand: denali: remove unneeded init of ECC_ENABLE register

The ECC correction is properly enabled/disabled before the page
read/write.  There is no need to set up this at the beginning of
the probe.

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