mtd: nand: sunxi: avoid retrieving data before ECC pass

The in-band data are copied twice: before ECC correction and after the
ECC engine has fixed all the fixable bitflips.
Drop the useless memcpy_fromio operation by passing a NULL pointer when
calling sunxi_nfc_read_buf().
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/sunxi_nand.c

@@ -586,7 +586,7 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 	if (*cur_off != data_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, data_off, -1);
 
-	sunxi_nfc_read_buf(mtd, data, ecc->size);
+	sunxi_nfc_read_buf(mtd, NULL, ecc->size);
 
 	if (data_off + ecc->size != oob_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);