mtd: omap3: nand: report corrected ecc errors

The number of corrected ECC errors should be reported since other MTD
systems make use of this information (such as UBI data scrubbing).

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>