mtd: mxc_nand: move ecc strengh setup before nand_scan_tail

commit 4a43faf54e9173b6acce37cf7f053fc9515a2cdf upstream.

Since commit 6a918bade9dab40aaef80559bd1169c69e8d69cb, the mxc_nand driver
fails with:

Driver must set ecc.strength when using hardware ECC

This is because nand_scan_tail checks for correct ecc strength
settings, so we must set them up before nand_scan_tail.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>