mtd: mxc_nand: remove duplicated ecc_stats counting

commit 0566477762f9e174e97af347ee9c865f908a5647 upstream.

The ecc_stats.corrected count variable will already be incremented in
the above framework-layer just after this callback.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>