mtd: mtd_nandecctest: add single bit error correction test

This adds the single bit error correction test case listed below:

Prepare data block without corruption and ECC data with single bit error,
and verify that the data block is preserved by __nand_correct_data().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>