mtd: nand: gpmi: may use minimum required ecc for 744 oobsize NAND

By default NAND driver will choose the highest ecc strength that oob
could contain, in this case, for some 8K+744 NAND flash, the ecc
strength will be up to 52bit, which beyonds the i.MX6QDL BCH capability
(40bit).

This patch allows the NAND driver try to use minimum required ecc
strength if it failed to use the highest ecc, even without explicitly
claiming "fsl,use-minimum-ecc" in dts.

Signed-off-by: Han Xu <b45815@freescale.com>
Acked-by: Huang Shijie <shijie.huang@arm.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>