mtd: nand: sunxi: fix sunxi_nfc_hw_ecc_read/write_chunk()

The sunxi_nfc_hw_ecc_read/write_chunk() functions try to avoid changing
the column address if unnecessary, but the logic to determine whether it's
necessary or not is currently wrong: it adds the ecc->bytes value to the
current offset where it should actually add ecc->size.

Fixes: 913821bd ("mtd: nand: sunxi: introduce sunxi_nfc_hw_ecc_read/write_chunk()")
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>